Hi,

What´s the difference between a semisynthetic 10w-40 oil for a car engine and a semisynthetic 10w-40 oil for a motorcycle (XT) engine.

I´m beginning to suspect that they are basically the same fluid in two separate canisters, only the bike-one is much more expensive.

Am I right or wrong? Can I run my 1VJ on car oil instead?

(I´m gonna get hanged by the oil companies now for sure...)

Regards / RtS

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Rikard the Swede

Hi car oil is for engine only not gearbox & clutch. If you use car oil you could end up with clutch problems or oil will have shorter working life as it is in gearbox

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2005 TT600re

Hi,

I have taken a more than healthy interst in this question and have conclude that for our bikes car oil is fine as long as fully synthetic is avoided.
Semi-synthetic car oil has never caused any of my bikes clutch slip problems over many tens of thousands of miles.

The usual reason given for needing to spend the extra and buy propper motorcycle oil is tha it contains a magic additive that better resists the shearing action of our gear boxes, but the following link seems to disprove this

http://www.ducatimeccanica.com/oil.html

Mark

yamaha's owner manual says:
use SAE 20W40 SE-specification
nowadays SE is almost the worst you can buy.
so if you use SF or better you are always on the safe side, no matter what type of oil.
any mineral oil will do. of course it won't harm if you use high-tech oil (synt., semi-synt.), pressumed you have too much money in your wallet.
i use mineral car oil since more than 260 tkm on all of my bikes with no bad experience at all.

best regards
klaus
xt600.de / tech. dep.

oils are made from a base oil improved with additives. the higher the "synthetic" claim, the more of the "base oil" is replaced by "harder" man made or improved fractions... therefore fully synth is fully man made / processed. this has naff all to do with "bike or car" applications. (and is instead looking for air release, shearing (from gears), heat, acid and base resistence (not an exhaustive list my any means) - the longer the oil remains in good condition, the longer it does its job. obviously this is important in highly tuned engines, (Race and high revving road).
my personal rule of thumb - if most of the time is speant below 8K (on bikes), use mineral, above use semi, if racing (not track days) use fully synth.

the clutch probs come from friction reduction additives that are added to car oils - these esters (i think) bond to the internal surfaces to provide another molecular layer of protection. If your bike has a wet clutch (one which runs in the engine oil) these additives bond to this as well, reducing the coefficient of friction of the clutch, (not what you want - causes slip).
Bike oils leave out this additive. that is the only difference (well, it was in the world leader oil firm i worked for). If you have a dry clutch (ducati's and all cars) this isn't an issue as the oil doesn't come in contact with it. a newer clutch is "rougher" so will resist it more. If you ride gently you will notice it less, BUT the damage is still done.

had a boss who owned a training school who proved this theory brilliently. 10 bikes, bulk car oil (despite advice!), all get a service, all need new clutchs due to excess slip within a week!

so, IMHO. for 99% of the bikes on this page there is no point buying anything more than mineral bike oil. change it often (when it needs it not when the book says!). Most important: Always keep it topped up (will make it last far longer as it has longer "recovery" when your engines working)

and no, the price difference is not justified.

gosh, rant, sorry! hope it answers the question though!

dan

"I´m beginning to suspect that they are basically the same fluid in two separate canisters, only the bike-one is much more expensive."

In some cases this is realy a true! So do yourself a favour and obtain Motul or Silkolene semishynt ESTER based oil, so you can not miss! Unlike Motul and Silkolene, most of other synt oils are just MC oils, usualy used in automotive range.
AnteK

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AnteK