Synthetic OCI?

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Jun 11, 2003
Central Illinois
Hi all, I'm thinking of switching from dino to synthetic in my mother's 2000 Grand Prix with 60,000 miles on it. (3.1L V6) The car was bought brand new and has always had 3,000 mile changes with regular dino oil. I have also been using Mobil-1 in my 2000 Sonoma (2.2L 4-cyl) for 30,000 miles on 6,000 mile change intervals. It now has 74,000 miles on it. I also just recently switched over to Mobil-1 in my wife's 2000 Impala (3.4L V6) it has 77,000 on it. I plan on doing the first synthetic change at 3,000 miles and then 6,000 miles ever after. My question is, is 6,000 miles a reasonable change interval? Or could I possibly get more? I use Wix filters on all of the above cars. Thanks... Tony
I think 6K will prove to be about the right interval with the Wix filter and no additives. A uoa will tell for sure and be an opportunity to check for the coolant leaks on the 3.1 and 3.4 also. Go 6K and uoa.
6000 miles would be an excellent interval for that vehicle and Mobil 1. You probably could get quite a bit more miles as well, but I'd recommend doing oil analysis in order to see for sure.
6,000 miles is a good interval. You should get a UOA done before you decide on a longer interval. I just got done running M1 6,000 miles in a 5.7 L Chevy in good condition. TBN was down to 3.7 which means there was some life left in the oil. I used Blackstone Labs with analysis interpretation by Terry Dyson. Terry's added interpretations was easily worth the extra price. Maybe not for every analyis but at least until you find out how your engine is doing, then also again if lab results vary a lot on later changes.
I used Mobil 1 5w-30 and Mobil 1 filters in my 2001 Honda with 10,000 mile OCIs (on the oil and filter) and never had a problem. The car ran like a champ for 70,000 miles...and then I sold it. The oil always came out looking dirty, but smooth, if you know what I mean. If it matters, most of the miles on that car were highway miles.
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