One of my friends offered to do oil change on my car... and I asked him what kind of oil is he putting... he said "15W40, good for high milage cars"... but that's not what the manual recommended... and we kept arguing back and forth who is right... so what does 15w40 will do to your engine? This case... my engine?

Well you both are right. Because this oil won't kill your car, this oil is good for cars that get used everyday. So in your friends case get high mileage. But then again if you don't want to put the oil in your car then don't do it.
And yeah. :P hope I was kind of helpful.

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Originally Posted by farfellow

One of my friends offered to do oil change on my car...and I asked him what kind of oil is he putting...he said "15W40, good for high milage cars"...but that's not what the manual recommended...and we kept arguing back and forth who is right...so what does 15w40 will do to your engine? this case...my engine?

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I had a 85 Volvo.. and I always used 15w40 once the car reached over 200 thousand km and the motor is still running fne when it reached near half million km. I would change the oil at aprox 5000 km give or take and sometimes add a bottle of oil treatment. The only downfall for using a heavier oil might cause hard starting during wintry condition but I don't think you live in area with -40 celius. If your car burns a little oil 15w40 is probably better. Now we have a 91 Civic A-B car and I use 15w40 and again sometimes I add a bottle of oil treatment in between oil changes. Overall, 15w40 is cheaper than 10w40 or 5w40. In regards to oil treatment I would buy Dura-lube oil treatment once a year for my cars. In my opinion I trust Dura-lube products over Slick-50 I found Dura-lube has really maintained my motors and transmissions to last over 300 thousand km and on for both my Volvo and Honda. Cheers :rolleyes:

Ps: if anyone finds there Transmission sluggish while the gear is shifting rather than wasting money on a bottle of cheap transmission fix I would highly recommend using a bottle of Dura-lube transmission, while changing your tranny oil. Once this is done and after a hundred km of driving you can feel the difference.

Like Honda, I recommend SAE 5W-30, preferably full-synthetic. 15W-40 will reduce gas mileage; increase engine temperature, because of greater resistance; be harder to start, especially in winter; be harder on your battery and starter motor; and likely contribute to premature valve wear.

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Originally Posted by TxGreaseMonkey

Like Honda, I recommend SAE 5W-30, preferably full-synthetic. 15W-40 will reduce gas mileage; increase engine temperature, because of greater resistance; be harder to start, especially in winter; be harder on your battery and starter motor; and likely contribute to premature valve wear.

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Hi Texas... I agree for these small Honda engines it is prob best to use full syn oil:)

Thanks everyone for the answers! :) really help weight out the odds...

I'd say your friend is right!.
15w-40 every time for high milage, it will get the most out of the engine..