- Jul 8, 2002
- Lake Anna, VA
I told the girlfriend I would change her oil today in her 99 Mercury Cougar with the 2.5 DOHC V6. Her manual calls for 5W-30 but I was wondering if there would be any adverse effects of using 5W-20 instead? She drives alot of highway miles and I am gonna run an analysis to see how the 5W-20 holds up compared to the 5W-30 in there now. I know the 01 cougar's call for 5W-20 and the engine has not changed so I guess i've answered my own question but was looking for any additional comments.