Which is more fuel efficient 10W30 or 10W40 engine oil?

Technically, a lighter weight oil will provide better gas mileage as it’s lower viscosity makes it easier to move through the oil system. However, the difference between 10W30 and 10W40 will be indistinguishable.

What is 10W-40 oil used for?

Higher viscosity oil such as a 10W40 can be useful for older engines burning or leaking oil. We offer Mobil™ 10W40 high viscosity motor oils for use in vehicles with more than 75,000 miles, and a synthetic blend oil when cost is a consideration.

Is 10W40 good for high mileage?

A: Yes. This is a practical method to improve oil pressure in an older, highmileage engine. The slightly thicker oil film from the heavier base weight oil — 10W — can help protect worn engine bearings as well.

Will thicker oil damage my engine?

Some have even used thicker oil in a leaky engine to prevent oil from seeping out. But really, thicker oil is not good for your engine. Not when “thicker” means higher viscosity than the manufacturer recommends. Your engine was built to specific tolerances – spaces between the moving parts.

Should I use thicker oil in a high mileage engine?

Highmileage motor oil doesn’t hurt and it could prevent leaks from starting. Some mechanics recommend switching to a thicker (higher viscosity) oil — such as 10W-30 full synthetic oil instead of 5W-20 full synthetic — or using oil additives to stop leaks.