Honda Civic (06) Oil Viscosity

I just bought an 06 Civic w/ 101k miles. Honda says to use only 5W20 oil, but I used 5W30? Will there be any negative consequences from this–lower mpg or otherwise? Or is their guidance baloney?

Read your owners manual. My vehicle manual gives me the option of using 5W30 over 5W20. I don’t think it’s as much baloney as it’s a way to increase fuel economy which looks good on the factory specs of your Civic.

rtfm

The problem is that higher viscosity oil is bad for the engine at startup, which is when the majority of engine wear occurs.

5W30 will be virtually the same viscosity as 5W20 at startup.

I wouldn’t do another oil change, but the next oil change make sure you use 5W-20 from then on. It isn’t about start up. Your '06 Civic has the Vtec motor and the heavier weight of the oil in a hot engine is not providing the flow characteristics engineered into the variable valve mechanism.

You’ll get answers from both extremes here but the bottom line is to do what the owner’s manual says-period. Some will claim its just for MPG government calculations but others in the engineering field will say that things like bearing clearances and valves can be affected. I’ll with what the manual says which is 5-20.

I’m with Uncle Turbo. Just go back to the 5W20 the next time you change oil.

Having used 5W30 instead of 5W40 once will make no difference whatsoever.

Both base oil weights have a viscosity index (weight) of 5. The “post W” number represents the ability of the oil to resist flow (its viscosity) when it gets hot. This ability is accomplished by the addition of “viscosity modifiers”, which are microscopic coiled polymers that uncoil when the heat up and halp the oil resist flow at heat. The tradeoff is that the modifiers don;t have the same ability to lubricate, and as more oil is displaced with modifiers the ability of the oil to lubricate becomes reduced. In short, 5W30 maintains its viscosity when hot slightly better but 5W20 lubricates slightly better.

The difference is extremely minimal in context with all the other variables that affect the engine’s life. Minimal enough to be below measuring. Your engine’s wear at 400,000 miles will probably be the equivalent of what it would have been at 400,005 miles.

Now slap your wrist and go back to bed. You can sleep soundly.

Nice post the same mountainbike

Thanks, guys. I’ll switch to 5W20 next oil change regardless–that won’t be too long, because I change oil every 3k–don’t believe in this 7.5k stuff. Nor do I trust the oil usage readout.

Thank you Joseph.