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Best Engine Oil For Bikes

With the Covid lockdown and riding for pleasure banned for the duration here on the Isle of Man, I decided to service the Triumph Bobber myself. A quick search for the best motorcycle oil and it quickly dawned on me that things had moved on considerably since I last purchased a can of Castrol when I had my old pre-unit Triumph.

As I can’t be the only old biker (or novice biker for that matter) who’s more than a little lost looking at all the countless engine oil options, an idea for an article formulated and what follows is from Jamie, my go to guy for all things technical.


I grew up with bikes in the family. I remember attending the NEC bike show from about six-years-old, the numerous amounts of bikes and ‘bikers’ that would come round to the house, the weekends spent ‘tinkering’ with bikes (most of them were British so it was more a necessity than hobby), the little KTM scooter that we inherited as kids from ‘Great Aunt Nellie’ … I knew enough that when the oil light on my DTR flashed on, it needed oil because it was getting low. 

Fast forward a year or two, and when the engine oil light in my Mum’s new-ish Vauxhall Cavalier came on, I thought I had a few miles to find engine oil, same as my DTR. 

One +.020” crank regrind, set of big-end and main bearing shells, cylinder head gasket, piston rings and whatever else later, I’d learned a valuable lesson. Oil is the life-blood of any engine. If it wasn’t for the fact that Dad was a mechanical genius, capable of fixing anything, the car would have been scrapped. 

Did I mention that at that time, I was working for a well-known motorcycle tuning company? I really should have known better. I was a typical teenager with ‘shite between the ears’ as my boss might have said. On more than one occasion.

Which is the best oil for your motorcycle

So Which is the Best Engine Oil for Bikes?

What makes for the best engine oil for bikes? Does expense equate to quality? Can an oil be too thick? Should you change engine oil every 1,000 miles? What happens if you don’t change the oil regularly? … 

Engine oil is a complex subject, and for every different brand out there, there’s probably a hundred different questions, and depending on which expert you speak to, ten different answers per question. Some of the information is fact, some is preference, and the rest is … a bovine-related manure type substance. 

I’m an automotive engineer by trade, I’ve worked with engines, mainly performance engines, for around 25 years. This includes: 

  • Running my own performance car & bike company
  • Working with motorcycle drag racing engines
  • Building F1 and IndyCar engines
  • Being a Track Support Engineer (Engine)
  • Building WRC (World Rally Car) engines
  • Building Paris-Dakar engines
  • Managing an engine facility for a British performance car manufacturer 

… engines and engineering were my thing. (Today, I’m just a biffa that sits behind a computer writing about such). 

Am I the World’s Greatest Engine Engineer? Nope. Do I know every single thing about engines? Not even close. Do I know more than the average man in the street? Possibly. 

I’m definitely not the fount of all knowledge when it comes to this sort of thing; I’ve met a number of engineers that make me feel dumb when they’re discussing technical topics, but … I have a pretty good understanding. 

I have close to thirty years of experience both as an engineer (actually making & modifying engine components) and as a performance/race engine builder, with championship winning credentials. 

So, this is my view on all things motorcycle engine oil related. 


Let’s start with some basics. 

After an absence of around 8 years from being a spanner-monkey, you tend to forget what’s real, what’s a myth, and what is utter nonsense (to a degree). A quick search on ‘basic motorcycle oil facts’ tends to reveal that a large proportion of ‘facts’ are articles written by someone who clearly has little mechanical knowledge, and is looking for search engine traffic to their website. 

Either that, or an industry giant that just has one goal … “We’re the best damn motorcycle oil company, buy our products”. So how does the average Joe or Josephine know what to look for? How can they separate the wheat from the chaff? Or the Mobil 1 from the Poundstretcher Special?

Why Does a Motorcycle Engine Need Oil?

Occasionally in life, we find something that is all the better for a little friction, and it’s not necessarily that

Think of grippy tyres, braking, some types of suspension or even microwaves; they all use friction to work at their best. 

Similarly, there are hundreds of processes that create friction as a secondary action. Some can be good – rubbing your hands together on a cold day to keep warm. Some not so good – joggers nipple for example.

Perhaps for most of us, we encounter friction daily through the use of a car or motorcycle; rotating crankshaft and cams, pistons, valves … all rotating, or reciprocating in some form, metal on metal. 

Of course, engineers have long understood the forces involved with anything like this. They try to counter these forces and frictions through material engineering or design; bearing shells, thrust off-set, platings and coatings. 

However, despite the clever engineering, we still need engine oil, and it’s more than just slippery stuff that helps reduce wear. The oil has a secondary purpose, which is to carry contaminants away from the system and trap them in a super-fine mesh, also known as an oil filter. Makes sense, right?

A quality oil filter is just as important as using a quality engine oil

If you were to let contaminated oil flow around an engine, it would be like having a fine grinding paste just working its way around, resulting in premature wear of all components. 

Basics of Motorcycle Engine Oils part 2

If you’ve ever stood and looked at the vast array of different types of oil, and wondered to yourself “is there really that much difference?”, then the answer is simple; no.

Yes. Sort of. 

As well as specific motorcycle oils we have different weights, single grade, multi-grade, mineral oils, semi-synthetic, fully synthetic, cold weight, hot weight, diesel specific, 2 stroke specific, classic bike and classic car specific and then there’s all the various race oils. (Speaking of classic, who remembers the unique smell of Castrol R?). 

To answer the question of difference, or lack thereof, imagine this: you’re on a haul with your bike, and for whatever reason, it has dumped the contents of the sump, there is no oil whatsoever circulating in the engine. Yet a super helpful person comes along and tells you that he has 5 litres of ‘diesel special’ in his boot, and did you want it?

Forgetting the whole ‘where did the oil go?’, ‘has it coated the rear tyre?’,’ I need a funnel’ situation, then I’d be happy to drop it in the bike if it meant I wasn’t waiting an hour or two for the recovery truck. 

Of course, I’d make sure that it was replaced at the next earliest convenience, but it would work well enough to get me there. So there isn’t that much difference. 

Would I leave it in for the regular period of time? Nope. Would I ride everywhere with the tacho needle buried in the red line? Nope. Equally, would I be worried about wear and tear and the engine popping and scattering its internals all over the carriageway? Again, the answer is an emphatic ‘nope’. 

So just what gives?

There is one situation that I’d be very wary of, and it’s quite possibly the opposite to what you may be thinking. If I had a motorcycle engine that was running on mineral oil (an old classic for example),with high miles, I would do everything to avoid giving it a drop of the good stuff in the form of fully synthetic oil, because there’s a high chance that the bores would glaze up, leading to the situation where the engine starts burning oil. 

Some engineers may agree/disagree with that statement, but along with it ‘being known’ in my professional capacity, I’ve experienced it personally. 

Society of Automotive Engineers (SAE) & What Those Numbers Mean

5W 30, 10W 40, 20W 50 … there are as many different weights when it comes to oil, as there are manufacturers, but what does the whole ‘weight’ measurement mean?

The weight of an oil, also known as the grade, specifically measures the thickness of the oil, or the viscosity, at around 100 degrees Celsius (the normal-ish operating temperature of an engine). The smaller the number, the faster flowing it is. Most engines can take a small variation from the manufacturer’s recommended specification, particularly if you’re in extremes of weather, but it isn’t a free for all. 

It’s also worth noting that changing the weight of an engine oil could affect other systems, and processes like fuel economy. Please don’t think you know better than the manufacturer, unless you really do!

The first number always ends with a ‘W’ – which stands for ‘Winter’, although of course, the reality is that it just means when it’s cold (the engine oil). You’ll notice that the cold weight is always lower, which means that on cold start-ups, the oil flows quickly through the system, lessening the chance of any damage from a cold start. 

A very general rule of thumb is that the older the engine, the thicker the engine oil. Manufacturing tolerances weren’t what they are now, so instead of dealing with microns and tenths of thousands of an inch, you could be looking at just thousands of an inch, and that can make a huge difference to oil pressures. 

Think of it like a garden hose pipe; with no end on the pipe, the water flows freely but at low pressure, if you squeeze the end of the pipe, you have a jet of water with higher pressure, which sprays much further. The same applies to manufacturing tolerances in oilways – too big a gap, and the oil will struggle to make it round the system, often leading to premature failure at the farthest point – the top end of the motor. 

Mineral and Synthetic Motorcycle Oil – What’s The Difference?

How do you know whether you should be using a mineral, semi-synthetic, or full synthetic motorcycle oil?

Again, there is a general rule here also – mineral = old, full synthetic = high performance/race, and semi-synthetic is a bit in-between. But of course there is more to it. 

You could say that semi & full synthetic oil are more slippery (slippier?), it’s for this reason that most engine builders don’t use them after a full engine rebuild, preferring to do the running in period with a simple mineral oil, which allows for the components to bed in properly. 

This is also why adding a full synth to a high mileage engine (that doesn’t normally run on fully synthetic) tends to glaze the bores up. It’s just too damn slippy. 

Essentially though, the differences between the oils is thus:

Mineral Engine Oil

Mineral oil is made from the refining of crude petroleum, with natural contaminants and unwanted hydrocarbons removed as part of the process. 

They generally don’t offer as much protection (although this is engine dependent), need to be changed more often, and are cheaper (thanks to the lack of additives). 

Synthetic Engine Oil

For this example, I’ve taken the wording straight from the source – Total Oils:

Primarily designed for high-performance engines, synthetic motor oils are a product of complex chemical transformations that are performed either directly on drilled crude petroleum or using preselected molecules. The difference with mineral oils resides in the transformation process: synthetic oil undergoes more sophisticated modification.

Key points on synthetic engine oil:

  • They contain fewer impurities than mineral oils
  • They are chemically modified

For both types of engine oil, additives are included to significantly improve their performance. These additives can protect against wear, oxidation, corrosion, or foam, or provide detergent or dispersant effects.

Semi-Synthetic Engine Oils

It’s not hard to understand that the semi-synthetic oil are somewhat of a middle-ground, and you’ll find them in use in the majority of internal combustion engines … a good all-rounder. 

Pricing up your Motorcycle Engine Oil

Is it necessary to buy the best motorcycle oil or can you run your engine on a ‘Happy Shopper’ special at around £3 a litre?

This is where we’re now starting to come more into the motorcycle oil territory; modern internal combustion engines have progressed in leaps and bounds in the last decade or so, thanks mainly to stricter MPG and emission legislation. 

This means that car engines aren’t quite so lacklustre, or behind the times, as they once were when comparing them to bike engines. For example, my old ZZR14 made near enough 200hp, from a naturally aspirated 1.4 litre engine. 

Car engines still don’t (generally speaking) replicate that level of performance, certainly without attaining the same level of reliability, but they’re closer than they ever have been. 

In the car world, it wasn’t that long ago that 100hp/litre was considered as pretty racy (naturally aspirated), but that figure has been pretty standard for bikes for a long time, even on something that wasn’t necessarily considered as a sportsbike. 

So even though we may consider certain motorcycles to be ‘cruisers’, ‘tourers’ or just … ‘shopping’ bikes, at their heart lays some pretty powerful performance. 

Some of that performance can be designed in, or as a by-product of the design; small CC motors, using a short stroke and small diameter piston can be revved much harder – it’s not unheard of for a small engine to be revved to 18-19,000 RPM, and what’s the average car? 6 or 7,000 RPM?

Aside from revving higher, and the advantages that brings, a motorcycle engine is closer to what I would call a ‘blueprinted’ engine – properly lightened and balanced crank & valve train, smaller tolerances, higher compression, matched volumes (in the cylinder head and piston) … everything that I used to do for a road engine, came pretty much as standard with Japanese (in particular) bikes. 

So we know that bike engines produce good power, and relative to their size, they’re the equivalent of a race car, is it worth spending that extra money on decent engine oil?

I believe it is.

Most of the higher end brands have invested millions in technical development, getting their motorcycle engine oil to work at the extreme end of the spectrum – going into detail with ‘shear’ stress (where the oil is almost being ripped apart), stability, longevity, cleaning, and even performance. 

Similarly, bike engine designers do the same – small touches that you’ll never know about, or even care about, that may only make the tiniest fraction of a difference … it’s those tiny fractions that work together. 

As an example, if you’ve ever seen a crankshaft, you’ll know that it’s a pretty big lumpy bit of metal, with counterweights opposite the journal pins (for the connecting rods). 

But high-performance engines shave those counterweights into a ‘knife edge’ shape to help cut through the air/oil mixture in the crankcase. It’s an expensive process, and certainly one that wouldn’t make a world of difference, but worthwhile doing when you’re looking for performance. 

Equally, much of the oil galleys have been designed to avoid sharp angles that could slow the oil flow – something that would be done on a blueprint, but not necessary with most bike engines. 

There are hundreds of design touches and improvements, all as standard. 

I’m quite happy throwing any old oil (providing it’s semi-synth) in my daily driver of a car, but when it comes to my motorcycle oil, I’m a little more fussy. 

Which brings me to my next point:

Should I Stick with the Manufacturers Recommendation?

It would be a brave person to go against the engineers of a product, in the belief that you know best, wouldn’t it?

For the main part, I’d always stick pretty close to the recommended oil WEIGHT, but not necessarily the brand. Of course, if I was to decide on a road trip to Siberia, or the North Pole for example, I’d change oil weights. Perhaps if I was heading somewhere like Death Valley (average temperature in August of 46 degrees Celsius), again I’d look to change it, but aside from that, your manufacturer knows better than you. 

And if the worst happened, don’t think that they couldn’t tell that you’ve monkied about with your engine oil – it’s super easy to get an analysis done, both of the engine oil itself, and the components inside the engine. Believe me, I’ve done it. 

You should also remember that motorcycles do need engine oil that’s specific to motorcycles, although as I mentioned before, in a pinch, I’d use any type of oil (barring cooking, coconut, olive or baby!). 

The reasons for this mainly stem from the clutch/gearbox setup on a bike, versus how they work in a car. 

Most motorcycle engines, certainly anything from the 1970s onwards (so excluding pre-unit Bonnies and the like) have the gearboxes and wet clutch fitted within the engine itself. Whereas a cars tend to use separate gearboxes and dry clutches (yes, I realise that some bikes do also, but they’re the minority). 

What this means is that motorcycle engine oil takes more punishment than the oil in a car – higher revving, more load through the gearbox, and of course, further additives for the wet clutch. 

It’s true that some riders will tell you that they’ve never had an issue with using car oil, but would they necessarily know? Are they stripping the engine and gearbox to measure wear? Or do they actually mean that their engine/gearbox or wet clutch has never exploded after using car oil?

Some years back, I owned a Kawasaki ZX9R, undoubtedly I would have topped up the oil with regular car oil (as I had an abundance of it on tap). It suffered with a gearbox failure, and the cost to put right (I wasn’t messing with a gearbox) was expensive, to say the least. 

I happen to know that those ‘9s’ suffered with gearbox problems (I learnt after the fact), but did I exacerbate the problem? Or perhaps speed up the failure process? I’ve spent my life inspecting mechanical components and building high horsepower engines, but I honestly couldn’t tell you. 

Who Makes the Best Motorcycle Engine Oil?

Top brands like Castrol spend fortunes on engine oil development

How long is a piece of string?

The honest answer is that there are so many factors to account for, that giving one simple answer is almost impossible; we’ve touched on the fact that I wouldn’t use a fully synthetic oil in a high mileage or very old motor. Equally, I wouldn’t put a standard, single grade mineral in a performance engine. 

The real question should be “Who makes the best engine oil for your bike?”

For me personally, I’m quite happy using a wide array of different brands, including some home brands such as Halfords, but with that said, when it comes to performance engineering, I’d stick with the better known brands. 

The reason for this is simple: development. 

It’s entirely possible that cheaper engine oils would work OK, perhaps give you the same level of protection as other brands, but it’s the same story with anything that’s aimed at being cost-effective; they’ll work for 80% of the applications, to a standard that’s ‘good enough’, but that’s it. 

When I was younger, I rode fast bikes, fast … like my hair was on fire. I did numerous trackdays, been around ‘The Ring’ a few times, and thought nothing of pulling prison speeds where I thought it appropriate. (OK, maybe ‘appropriate’ isn’t the exact right word, but what I’m saying is that thought always went into my riding, and the speeds I rode at). 

I spent a great deal of time and money on making my bikes exactly what I wanted, including remapping, performance parts, rideability etc. If I was looking for the best it could be (for me), why would I a) risk that for the sake of a few pounds, b) lessen the potential performance by fitting under-developed parts or fluids?

The topic of motorcycle engine oil is quite subjective, or in any engineering/ automotive industry – I can recall a number of engine failures with race cars, all using a certain brand of oil, and the analysts all came to the same conclusion … they failed due to this particular brand of oil. And yet, a little more investigation proved otherwise (turned out to be a harmonics issue, setting up a chain of events at a very specific RPM). But that brand of oil was never used again. 

How Often Should You Change the Oil in your Bike?

The performance engineer in me wants to tell you that oil change frequencies are strict, that you shouldn’t go over the requisite mileage/age before a change, and that in doing so, you’re risking enormous or expensive danger and/or repair bills. 

The lazy fat man that sits behind a computer all day wants to tell you a different story though; my daily runaround has been owned by me for the last (nearly) five years … the longest I’ve ever owned a vehicle. 

Having checked my mileage today, it seems that I’ve done around 50,000 miles within that time, and I’ve changed the oil precisely twice (today in fact is the second change, so that’s really only once in the last five years). 

I’ve pushed a borescope through the engine, and around the sump, its emissions are way less than an MOT standard, it has performance like new, and doesn’t clatter or rattle anymore than it should. Does this mean that regular oil changes are just a con?

Maybe the word ‘con’ isn’t correct? Does this mean that regular engine oil changes aren’t quite as vital as we’ve been told?

It’s a fact that engine oil does degrade over time, even when it’s standing in an opened bottle and not circulating in an engine. It’s also a fact that it carries a lot of contaminants away from the vital parts of an engine, and that an oil filter won’t generally filter out the combustion pollutants. What we don’t really know is the level of degradation, and in what time period. 

We also know that most oils contain additives that help to not only lubricate, but to clean the surfaces they come into contact with – when your oil is turning black, it’s showing that it’s working. So it’s worth changing it regularly, to keep it cleaning and lubricating to its full capacity? Absolutely.

Does it need changing every 2,000 miles? I personally wouldn’t. And yet, I’ve spent quite a bit of time in the United States with the IndyCar series. I have contacts over there, and there’s a few social media doodahs that I interact with, and I regularly see questions about changing oil within a 1,000 miles or two. It’s such a big business in the U.S. that there are drive-in oil change establishments, and they’re popular. 

So is it education? They’ve grown up with their muscle cars, which were never really that muscle-y, and been told that they positively need to have their engine oil changed every few months? Us Brits just expect it to never be touched until we have a regular service. 

Some manufacturers of extreme vehicles (both bikes & cars) recommend shorter service intervals, and at which point they’ll do an oil change, but that’s not necessarily dictated by the longevity or lifespan of the oil. 

A number of factors come in to play here – brake fluid is hygroscopic, which means it absorbs moisture from the air, brake pads can be worn down quicker, drivetrains take an incredible beating, suspension and tyres work overtime, and of course, the engine (usually) gets a good workout (aka: thrashed to within an inch of its life). 

Regular oil changes can help with engine life, they can help to prevent damage, and they can help with emissions. But … all engine oils are better developed than ever, longer lasting, have more additives, and are better engineered, so perhaps changing them every six months isn’t quite as necessary as it once was. 

How often should you change motorcycle engine oil?

Best Engine Oil for Your Motorcycle

We’re going to end this by answering the question that’s asked in the title – “What’s the Best Engine Oil for Bikes?”

Simply put, whatever it says in the owner’s manual, or the next best thing, whatever your oil specialist recommends. I’ve added that secondary statement because a number of oil companies now offer personal interactions.

More often than not, there will be a newer/better product on the market if your bike is more than a few months old, and the specialist will be able to advise you as to why their latest engine oil will work better for your motorcycle. 

Despite everything I’ve said about me being lazy, or too cheap to change my engine oil regularly, when it comes to my bikes, especially sport bikes, I’ll always try to at least take guidance on how often it’s changed. Yes, I’m an engineer, but if my engine popped because of an oil problem, I’d be a bit miffed … I’m no longer the young fool driving around (and wrecking) his mum’s Cavalier, I’ve learnt my lesson. 

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