1991 GMC Sonoma Engine oil

Tiny
MIGUEL LOPEZ
  • MEMBER
  • 1991 GMC SONOMA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
I have a GMC Sonoma 1991 4x2 4.3L, V6. I changed the engine few years ago, but "new" engine has 120000 miles already. Is working fine, I take good care of it. My question is: What kind of oil should I use in this high mileage engine? I have been using 10-40 all the time but wonder if I should change to another oil. Can I use synthetic or do you think it's not recomended in this old car? I live in Florida, hot weather. Thank you very much for your help.
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Sunday, November 22nd, 2009 AT 11:09 AM

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Tiny
BLUELIGHTNIN6
  • EXPERT
Definitely do NOT switch to synthetic now, it will only harm the engine since it has never had it in it before. You can stick with the same weight, I would suggest using the oils made specific for high mileage motors though, such as Castrol High Mileage.
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Wednesday, January 13th, 2010 AT 2:29 PM
Tiny
MAXIMILIAM
  • ADMIN
Well the factory oil would be 5W/30 and a step up to a 10W/30 wold be fine with the higher mileage. The 10W/40 should be fine.
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Tuesday, July 16th, 2013 AT 2:44 PM

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