Car 10w 40 oil ok?

[DomP]

Hi folks, if my oil is running low is it OK to use car oil of the same grade just for a top up?

[timwilky]

any oil is better than no oil

would I do it. No. Buy motorcycle grade oils with the correct additives/modifiers.

[maviczap]

Emergency top up only, as Tim says

[Red ones]

Car oils tend to have friction modifiers added to them. It helps reduce engine wear and improve fuel consumption.
Bike oils don't because the oil, unlike in a car, also sloshes around the clutch and reduction in friction there renders the clutch useless.

[timwilky]

My thoughts, and therefore probably not fact as I have been out of the industry for 30 years. But is not just the friction modifiers, but unlike modern (I say that because of the likes of minis/maxis etc) cars, motorcycles share their oil with the gearbox. Car engine oils are not designed to cope with the shearing & foam inducing action of a gearbox and could degrade as a result.

[Bibio]

if its needing a top up then its probably near needing a change so topping up with car oil will be ok, dont do it to often though.

[wideguy]

I've never used anything but engine oil made for cars in my motorcycles, and never had any problems. I change oil and filter at 3,000 miles if using mineral oil, 4,000 for full synthetic, which is what I almost always use.

[johnnyrod]

I used to use car oil years ago but I know of people who have had clutch problems - I never did. A little top-up wouldn't hurt if it's all you can get hold of and really can't wait any longer.

I question the belt-and-braceness of the service intervals - in my opinion, an oil change in the 21st century any more often than 6000 miles is costing money for no real benefit.

[atassiedevil]

I'd be more concerned why you aren't in a position to locate any of the correct type of oil. Surely somewhere sells it nearby?
Most BP/Shell places have 10/40 semi motorcycle oil on the shelf.

[ophic]

can't even get 2-stroke oil at my local garages. You're royally stuffed if you run out in the middle of the night round here. Fortunately I only need it for my chainsaw.

[speedyandypandy]

They've been researching these things for a 100 years++ I think there is a very good reason it's called motorcycle oil and automobile oil, there are also individual tests they need to pass, wich funny enough is based on what motor they go into.
And I wouldn't use anything else than one of the top brands, but that's just out of love of my bikes.

[Red ones]

They've been researching these things for a 100 years++ I think there is a very good reason it's called motorcycle oil and automobile oil, there are also individual tests they need to pass, wich funny enough is based on what motor they go into.


I'm sure they have also researched shampoo for years, but I can't work out why women have different shampoo from men.

[DJ123]

So long as the oil is the correct spec for your bike, that's all that matters. By which I mean the ACEA rating (as well as 10W/40), most bikes will be A3/B3

[Phoenix22]

All bike manufacturers with the exception of those with seperate gearbox & clutch specify a JASO MA1 or MA2 rating. These contain specific (& expensive) additives to protect against the shearing effect of the gearbox and are free of friction modifiers that could potentially cause clutch slip. Of more concern is potential gearbox damage by using a car oil due to the gears pitting. Also, research has shown that even a quality 'car' oil (Castrol) loses about 20% of its higher viscosity rating in about 800 miles if you use it in a motorcycle so your 10/40W effectively becomes more like 10/30W which is not good.

Now at risk of opening a can of worms you are now faced with the choice of JASO rated oil or 'equivalant to JASO' oil. To get a proper JASO approval on your oil costs money so this goes some way to explaining why motorcycle specific oil is more expensive. You can get cheaper equivalant to JASO spec from Halfords or Wilco for example but this stuff is made by Comma & has no JASO accreditation whatsoever, they just say it meets the standard.

Having said all that, any oil is better than none so a top up with it shouldn't cause any problems.

[johnnyrod]

Hooray! Facts!

[SvNewbie]

Also, research has shown that even a quality 'car' oil (Castrol) loses about 20% of its higher viscosity rating in about 800 miles if you use it in a motorcycle so your 10/40W effectively becomes more like 10/30W which is not good.


That's interesting. I wonder why it is so bad for the oil to be used in a gearbox when a gearbox oil change is such a rare even in a cars life. Often reaching the scrapheap with the same oil in the gearbox.

Do you have a reference?

[Bibio]

its a 'top up' its not like the OP is going to use it as an oil change. the OP probably has some car oil kicking about and needs to top the bike up. i would rather top my bike up using car oil than not top it up and run the risk of a feked engine. as long as the OP does an oil change using bike oil later on then all will be fine.

unless your bike is eating oil then a top up is usually near the service interval so its not going to be in there long. if your topping up a few times before the service then your bike need looked at or your ragging the complete shizz out of it all the time. so if the bike is that feked that you need to top up all the time then who cares what oil you use as the engine wont last much longer anyway.

[ophic]

That's interesting. I wonder why it is so bad for the oil to be used in a gearbox when a gearbox oil change is such a rare even in a cars life. Often reaching the scrapheap with the same oil in the gearbox.

Do you have a reference?
Gear oil is different and doesn't get nearly as hot.

[timwilky]

That's interesting. I wonder why it is so bad for the oil to be used in a gearbox when a gearbox oil change is such a rare even in a cars life. Often reaching the scrapheap with the same oil in the gearbox.

Do you have a reference?

It is the shearing effect that gears have on a lubricant. It will degrade a car multigrade, whereas true gearbox oils, are designed for this environment.

[wideguy]

For most of it's life, my '81 CB900F has run Mobile 1 automotive oil, changed at 4,000 mile intervals. I don't know about the first 12,000 miles, as that's what it had when I bought it, but it has 80,000 miles on the odometer now, including a season of racing and a few random track days. I tore it down the winter before last because the hard rubber on the cam chain guides was disintegrating and filling the engine with shredded bits. There wasn't any pitting on the gears, or any measurable wear on any transmission parts. There is still visible crosshatching on the cylinder walls, and it uses very little oil, considering its an air cooled engine that gets run pretty hard. The bearings were all in fine shape. Just anecdotal, but it works for me.

[DomP]

Wow I really started something here! My reason for asking was purely as Bible said, I could do with a top up and as my nearest motorbike oil seller was 20 miles away (living in Herefordshire has its drawbacks) I thought I'd pose the question. I would use motorcycle oil for what it costs as my bike only takes 1ltr from empty in normal circumstances.