Car vs. Motorcycle Oils
We've been told over and over that we shouldn't use auto oils in our motorcycles. The usual reason offered is that our bikes are air-cooled and car oils aren't designed for that use. But there have been air-cooled autos, and they use car oil! So what are the differences between car and bike oils? You can ask the oil makers and you'll come away with the feeling you've been talking with a snake oil medicine show dude. They will not give you a straight answer.

In theory the base oil stock should be as pure as possible in either case. While there might be some differences, it would seem the oil companies would then tout those differences. They don't. Generally they just point to the additive packages as being the difference. So what are the differences in the packages that makes one oil suitable for an air-cooled engine and another for water-cooled motors? I'll pick a few commonly used oils and list some additive levels. Obviously I'm not going to cover every oil someone might use, but you'll see a pattern. All are 20w-50, except the Mobil 1 15w-50 car oil.

M1 V-Twin Moly-91 Bo-255 Ca-2648 Mg-13 Ph-1683 Zn-1823
M1 15w-50 car Moly-79 Bo-281 Ca-2937 Mg-17 Ph-1223 Zn-1376
HD Syn 3 Moly-1 Bo-271 Ca-1342 Mg-740 Ph-997 Zn-1068
Castrol GTX car Moly-? Bo-0 Ca-1163 Mg-259 Ph-928 Zn-1133
Havoline car Moly-230 Bo-170 Ca-2461 Mg-66 Ph-978 Zn-1093

As a reminder:
Anti-wear - Zinc, phosphorus, molybdenum, manganese, potassium, and sodium.
Acid neutralizers - Boron, calcium, and magnesium.
Friction modifier - Moly.

See a pattern? If you do, you've got a better eye than mine. The pattern I see is there is no pattern. Some bike oils appear better than car oils. Some car oils are better than other bike oils. I see an $8/quart bike oil that has an excellent anti-wear package, almost to the over-kill point. I see a $5/quart car oil that appears much better than the MoCo $8/quart oil. Finally, in this short series, a famous car (dino) oil doesn't appear to look as good as the other examples. But another car (dino) oil, at about $2/quart, shows to be a superb oil.

Look at the examples, balance the differences in additive levels with price, throw in how often you change your oil, and draw your own conclusions.

Synthetics vs. Dino Oils
We know that synthetic oils cost significantly more than regular oils. Is the increased cost worth it? It seems to boil down to, "That depends!!"

Synthetic oil withstands heat better than dino oils. A temperature that will literally cook (oxidize) a regular oil will have no effect on a good synthetic. If you regularly ride in congested city traffic, participate in parades, or ride in an area where the temperatures are often well above 90º F, then a synthetic may give you years more use of your engine. If you ride a Twin Cam HD, remember your oil temperatures can be in the 250º F range. This is very close to the upper limit of dino oil, and you are going to experience increased oil oxidation, more shear, and the resultant decrease in viscosity. If you change your oil at intervals of more than 3000 miles, the inherent ability of synthetics to retain their viscosity better, will likely give you better engine longevity. If you change oil at 2000 to 3000 mile intervals, don't experience extreme temperatures in your area, and seldom "stress" your engine, then a synthetic may be more than you need.

Engine Break-in
One of the old wives' tales was you couldn't break in a motor with synthetic oil. It was said the rings wouldn't seat for one thing. It's been proved otherwise, but you'll still hear it every now and again.

If you go to several oil manufacturer's sites you'll see their responses to questions concerning break-in with synthetics. One of the sites lists about ten vehicles that come with factory fills of synthetic oil. Doesn't seem to cause a break-in problem with these vehicles, so why worry about it?

 

Skip,

Just took the time to read parts 1 & 2...awesome! Love this kinda techno-geek stuff.

Thanks for all of your time to make it available for us.

Rob

 

Thanks for all the great info. I think I'm "there" on the engine oil and the tranny.....but I'm still not settled on the primary. It would seem that I'm looking for a good anti-wear additive package without or minimal Moly as this is a friction modifer....which is not good for wet clutches.....am I tracking??

I do like the comparisons you give on the additive package values......so my question is this....where do you find this information??....I would like to find a reference for all oil products so I can review myself.....is there a website that would have such a list??

Thanks again!

 

Once again, beautiful sourced information! Thanks, Skip.

 

I've worked in the industry for 35 years formulating and testing diesel, passenger car and motorcycle oils. Maybe in a couple of years when I retire I'll give you some information from someone who really knows what they are talking about. For example, you have no clue what the boron and moly are used for - in terms of motorcycle performance they are not relevant. Second, phosphorus, not zinc is what provides antiwear performance. What's overkill. Unless you have run hundreds of tests how do you know? For motorcycles, 0.10 wt % is a good minimum and 0.18 wt % is just a really good antiwear/antioxidant level, just ask the NASCAR guys. And what about ashless dispersants, you don't even seem to know they exist and yet they make up as much as 50% of all additive packages. When you talk about Ca and Mg do you know whether you are talking about phenates or sulfonates, neutral or overbased. It makes a difference. For synthetics one of the most important selections is the ashless antioxidant you use but since it's ashless you won't see it in spectrographic analysis (just like ashless dispersants) so you don't even know they are there let alone how important they are. Most of what is out there on engine oils is, at best, half the story. Sorry, but you really don't have enough information to draw any conclusions.

 

Great post, some good info in there.

 

All in all, as Ive said all along, just use a damn synthetic oil. Ive always been a big believer in synthetic oils in air cooled motors just for the simple fact that it withstands the higher temperatures associated with an air cooled motor. For the rest of the mumbo jumbo I could really care less. Never paid any serious attention to it.

Few things to note, took some readings off of 3 different bikes this morning, a twin cam(mine), a EVO sportster(mine), and an EVO big twin(a friends). These temps were taken in 40-45 degree weather,a rather cool day. After initial engine warmup and a short ride through the country, I took a temp sensor gun and took the average readings of the engine temps. Even in cool weather during the winter, these bikes were showing temps in the 300-350 degree range in the heads and slightly higher in the cylinders themselves. All 3 of these bikes had oil coolers installed too. And the thermostats were activated. Oil temps get HOT in these bikes. And oil slowly starts to break down from day 1, even synthetic oil. Thats why I tell people to change their synthetic oil on regular "dino" oil intervals of about 2-2500 miles MAXIMUM or less if their oil turns color and starts to feel gritty. Even the synthetic oils experience viscosity break down. They just do a much better job withstanding it for a longer period of time, but they are far from immune.

 

I'm curious, why wait a couple of years? If it has to do with some requirement to maintain proprietary secrets, well, that certainly explains why we have only half the story. As consumers, we're left with no choice but to evaluate the information available to us. If those in the "know," such as yourself, continue to keep this information close to the vest, and then point out that we don't have enough information to draw conclusions, then I have to ask, how do we draw conclusions?? Trust the manufacturer's information? No, thanks.

For my part, I appreciate the information. The sources are cited, the information is presented as what it is, and while it may not be the complete picture, it certainly provides people with an opportunity to make a decision based on something more than "Ooo...I like the BLUE bottle!!" Just my $.02.

Thanks, again, Skip!

 

Sorry, somtimes I just get so frustrated with all the partial information and just plain wrong information that's out there I can't contain myself. Yes, it does have to do with information that really isn't proprietary but might be considered somehow by the lawyers as an offical company position and require legal review. You just have to love big corporations. Anyway, I'm not ready to bet my pension on their perception. But even if all the info was available it still wouldn't provide a great basis for decision making. For example, with the high VI of PAO synthetics it's possible to make 5W-20, 10W-30 and 20W-50 oils without using VI Improvers. Wider cross grades still require them. VI improvers are a necessary evil, they are very high molecular weight additives that have poor thermal stability and shear rapidly in service, particularly in transmissions. As far as I know only one manufacturer makes a non-VI improved 20W-50 but most use VI improvers but of course this is not indicated on the bottle and you need shear data (not readily available) to determine if an oil does or does not contain this type of additive. Since most people don't understand what VI improvers do, how they do it, and what are the pros and cons (mostly cons) of adding a very high molecular weight polymer to an engine oil are it wouldn't mean much to most people. I know this isn't an answer you want to hear but your best bet is to pick a company with good historic track record that you trust and stick with them. One of the major additive companies, Lubrizol, (no I don't work for Lubrizol), used to have a very good additive chemistry primer on their web page, www.lubrizol.com. You might want to check it our if you want to learn more about additive chemistry in general.

 

Thanks for the clarification and additional info, it gives us something else to chew over. And I would certainly be interested in whatever educational info you felt comfortable sharing, even though it might be quite esoteric. I'm a data junky sometimes.

I do understand your position in reference to potentially proprietary data, your company, and your pension, so I don't feel snubbed at all in reference to that sort of info. But if there's any clearly open source stuff you can share, or general background stuff, please feel free to post. Can't gurantee I'll understand it all, but that won't be your fault!

I'll definitely add the Lubrizol link to my reference group, things to study in the desert.

Enjoy the ride.