engine oil viscosity

[jaysta]

Hi

I was wondering if anyone knew about oil viscosity.

I need to do an oil change on my car and Dad's given me a load of oil that's spare from when he did an oil change on his car. I've checked the Haynes manual for my car and the spec oil for my engine needs to be 10w30 or 15w30.

The oil that Dad's given me is 10w40.

I'm wondering if it's ok to use... what do you guys think? I used to know what the figures meant but now not so sure.

My car is a Toyota Corolla 1.3l T'99 reg 45k miles
Dad's is a BMW 318i

Thanks for your time,

Jay

 

[davieboy]

10w30 is an american spec. very rare over here. 10w40 will be fine for a corolla. is it a good brand oil?

i could bore you of the differences between 10w30 and 10w40, but take it from me it will be fine (as long as its a good make, shell, texaco,etc)

 

[xerxes]

The first figure (10 or 15) is the SAE measurement of viscosity at low temperature, the second figure is the viscosity at engine operating temperature, when hot.

Sometimes it's an advantage to use a higher viscosity oil in a worn engine that is burning oil. However, it's likely then to consume more fuel, and given the high tax on fuel, not therefore necessarily a good idea.

If I were you I'd get the recommended multigrade oil for your car, and let your father use the other stuff for topping up his level. But I don't think it will do much harm if you decide to use the 10w40 in your own vehicle.

 

[Kes]

The first figure (10 or 15) is the SAE measurement of viscosity at low temperature, the second figure is the viscosity at engine operating temperature, when hot.

Not quite. The first figure (10W) specifies that the oil will behave as a straight SAE 10 oil would at low temperatures, I can't remember the exact temp, somewhere just above (water) freezing I think. The second figure (40) specifies that the oil will behave as a straight SAE 40 oil would at 100 deg C. So although the 40 figure indicates a 'thicker' oil, as we all know oil when hot is as thin as cat wizz. In any event the SAE grade bands are linear, and quite wide, so a high 30 is only a gnat's elbow away from a low 40. You don't know where the oil you're using is positioned in the bands, and it probably varies from can to can.

I'm surprised that you father had enough left over to enable you to change your oil. Still, I would go ahead and use it. I believe that 30 oils were introduced to enable engines to pass economy tests (I read that either Ford or VAG reduced their estimated engine life with the thinner oils). In the harsh light of reality your car is, like mine, worth peanuts, and this oil will not damage your engine.

PS A 10w-40 will be better than a 15W-30, as it is thinner at startup where a great deal of wear takes place, the oil needs to get circulating qickly, and as little resistance as possible is needed to start the engine. I always go for 5W or 0W if I can.

 

[tommydickfinger]

the answer your after jaysta, is yes- use the oil- dont bother with haynes and dont bother looking into it to far- or you'll find your head in a spin.
kind regrads

 

[jaysta]

Thanks for the replies guys

I decided to go ahead and use the 10w-40 and it seems better at the moment.

Jay