5W20 weight Vs 5W30 weight
 

Just bought an o8 Honda Civic LXthat, according to the owners manual, needs to use 5W20 oil. My old Honda used 5W30. Ive always used Mobil 1 for years with excellent results....my problem is I have a number of cases of 5W30 still left but don't know if I can use them in the new ride. Honda parts here said they didn't see a problem but then the service guy said I couldn't it would cause problems.The @008 Si calls for 5W30. I know the 5W20 came out to meet CAFE standards for mileage. Is there that much difference in the engines that would cause damage to my new ride if I did use the 5W30 synthetic. Any input would be greatly appreciated.....thanks guys

RE: 5W20 weight Vs 5W30 weight
 

I dont see what the problem this mechanic is trying to fabricate by scaring you not to use your 5w-30. Ive even used 10w-40 at times in my 01 civic ex, with absolutely no problems. The 30 part of it should actually protect more should your engine get hot enough, I understand. Pls correct me if I am wrong.

RE: 5W20 weight Vs 5W30 weight
 

Do you think the store you purchased the 5W30 might allow an exchange for 5W20?

RE: 5W20 weight Vs 5W30 weight
 

As long as your oil pressure is within proper range, and there aren't any funky additives missing/present, it'll be fine for a while. There isn't much difference between the two unless extreme temps exist. Heck, people have used ATF and gear oil in emergencies.

RE: 5W20 weight Vs 5W30 weight
 

you can either go with RonJ's idea of exchanging them if the store will let you or you can use them. I have a '03 Windstar that requires 5W-20 but for the first few oil changes, I went to Midas and they didn't give a rip about getting the right weight. They just used their bulk 5W-30 or 10W-30. I didn't realize this until a couple of years had passed. Ever since then I have done my own oil change and made sure I bought the Motorcraft 5W-20 synthethic blend. Haven't had any issues with the engine so far.

I believe you are correct, DickG, that the reason why so many new cars require the 5W-20 is b/c of the CAFE standards. But if you change the oil regularly, I don't see much difference. I think the real difference comes when you do not change the oil at regular intervals.

I'd see if I could exchange those cases first.

RE: 5W20 weight Vs 5W30 weight
 

5W20 is a lighter oil designed to reduce friction for the ultimate in fuel economy. It doesn't make a huge difference, i use 10W30 in my civic (97 civic mind you but my point is coming in the next few sentences) which has basically the same engine as the newer civics that require 5W20. It's really up to you and your vehicle needs. When it comes to oil weights i wouldn't go any lower than recommended, but i've never had an issue with going with a thicker oil.

RE: 5W20 weight Vs 5W30 weight
 

It will run fine. The difference is really not that big of deal. Maybe your machanic was just trying to scare you into a oil change or something.