The more miles an engine has the higher the weight the motor oil should have? 10W-40 on a 1999 Honda Accord?

Question

I'm confused like h**l right now. I have a 1999 Honda Accord V6 with 145,000 miles. Should the type of oil that you put in change as the engine gets more miles on it?

I have a friend that says I should put 10w-40 on it... The engine sounds fine, by the way.

The manual says 5w-30 or 10w-30 if it's not lower than 12 degrees outside. Does this oil type ever change? Should the oil viscosity change over time?

I'm confused... The car has 145,000 miles. What kind of oil should I put? No synthetic.

Answer 1

Just because of the miles that you have on an engine is not the deciding factor for what weight oil is used. I would go with a 10w-30 myself, but 5/30 should still work fine. The main differences are that 5/30 will allow for greater fuel mileage and "flow" through the bearing clearances better than a heavier oil. In the 70's an engine had 0.005 for a clearance for the oil to pass through, and now that number is 0.0015, a little more than 1/4th the gap. A 10/40 will not flow through those clearances when cold, and will give resistance when warm.

Basically, if you are not having a noise problem with the engine (such as a light tapping) or oil burning off, keep using the 5/30 for better economy and lower emmisions.

Answer 2

Unless you have a problem stick with the factory recommended oil. Even at 145 K miles your engine can be in good shape, so what's the point in making it work harder pumping higher viscosity oil?

Answer 3

Stick with the manual, and go with 10w30.  Heavier oil will reduce fuel mileage, and may not adequately protect all the critical parts in the engine, lubricated through tiny orifices.

Answer 4

no synthetic.  and no heavy oil  actually b/c of the additives in it, many companies won't warrant a car that has had 10-40 used in it now.

IF, and only if, your car is leaking or burning oil, you could go to the heavier oil recommended (10-30) and possibly a high mileage oil  (actually some companies make high mileage oil in a 5-30 now so it's a great option), but if not, there's no reason to change.  the only reason to go to the heavier oil is if you are already having problems, otherwise, if it ain't broke don't fix it.

Answer 5

Yes, as the car ages the heavier the oil should be. And during winter, or just before, you should change the oil to a lighter one.

For example 10w30 in summer, and 5w30 in winter, the reason is the oil will take longer to warm and flow in winter that in summer.  

Oil viscosity will change over time, so regular oil changes is required.  I do mine twice a year.