Oil viscosity for my 2010 Honda Civic

I just found out that my oil change guy has been using Castrol 10-W30 in my 2010 Civic 1.8. Honda calls for 5-W20. I have been about 15000 miles while using this shop. Has there been any serious damage to this engine by running with 10-W30?

I doubt it. If you check your owner’s manual, you may find that 10W-30 is listed as an acceptable oil for higher temperature conditions. And even if it isn’t, IMO the viscosity difference is not drastic enough to make much wear difference over 15k miles. Just go back to using 5w-20 and don’t lose sleep over it.

I would use 5W-20 in the future. If you live in a hot climate year round 10W-30 would be fine (Texas, FL, AZ, southern CA). If you live where winters get cold 5W-20 is best year round.

I suspect no damage done, you might have lost one or two mpg due to thicker oil. Reasons for 5W-20 is better fuel economy due to less internal friction in the motor. In the winter it is also much easier on the starting motor when 0W or 5W-20 oils stay thin at sub freezing temps.

Serious damage?! 10W-30 should be just fine for your engine. Your owner’s manual may even list this weight as perfectly acceptable to 5W-20, which is slightly preferred to reduce fuel economy by maybe 1 mpg, if that. Continue driving with your current oil until it’s time for your next scheduled oil change.

Steve is right, no damage at all, but maybe a very slight loss of fuel mileage.

I doubt there would be any engine “damage”, perhaps a litle accelerated wear. You’re fine but return to the use of the specified oil as soon as possible. The details of the variable valve timing system on your car elude me at the moment, but earlier Hondas had a system that was sensitive to sludging or too thick of engine oil causing sticky solenoids.

No damage, but switch weights on the next oil chenge. Find a new “oil change guy” too. While the engine has a high tolerance for the wrong oil being used, and as Steve said it may even be recommended for your climate, your transmission does not. If your current guy ever does the tranny fluid for your and execises the same complacency, you could end up with a very expensive problem.

By the way, is this a Quickie Lube?