So I know this is a much discussed topic but I could do with some advice on engine oil. I have an 89 c4 with 111,000 on the clock. The previous owner bumped the oil up to 10w40 but it is using quite a bit. Before I get into replacing seals and rebuilding engines I would like to do a simple oil change. Should I go with 10w40 with an addative like Lucas oil stabilizer/stop leak as a seal conditioner or bump up to something like 10w60 or does anyone have any suggestions on high mileage oils. Most of the info I can find related to US products which I can't find so any product reccomendations would be appreciated. Thanks in advance.
C4 oil
- Thread starter Ovie
- Start date
Mick Howes
CCCUK Member
As an 89,is this the LT1engine? If so, should be using 5/20 fully synthetic.
It's the L98, manufacturer reccomends 5w30, but that's a bit thin for the age and wear on the engine. I have my suspicions about it's valve stem seals but that's something I will get around to later.
Mick Howes
CCCUK Member
So very similar to the C3 L82, when I had my C3, before engine rebuild used 20/50 mineral (it was a bit of an oil burner then) after rebuild used 10/30 synthetic, it was fine with this. Problem with simply using thicker and thicker oil, just adding to the problems, seals etc getting worse with all that added pressure, best option is a rebuilt, or at least a top end overhaul.
Redlevel
Well-known user
Hi.
I have an '87 L98 with over 150k miles on it. It rarely needs a top up and Ive been using Mobil 1 10w60 FS (older car/high mileage/track day oil) for years. It gets changed every 15k miles or 2 years as the car is/was (I'm retired now) my daily commuter/holiday car since 2004.
Manufacturers simply specify a single oil grade to cover all temperatures and environmental conditions so a 5W is for those driving in conditions around -30deg, nothing to do with the quality of the oil, so to keep using it in the UK where the temp is very rarely -10deg is a bit naive. As C4's tend to run hot, I would prefer protection at a higher temp end rather than a lower temp hence my liking for 10w60 for those hot summer motorway thrashes down to freezing Bognor where my wifes family hails from! We live in SW Scotland where the climate is more temperate than some parts of the UK (Highlands/South coast etc).
5w30 Might be ok if you live and drive in -30deg, but it'll be short on hot weather protection, and our summers are getting hotter here in the UK. Last year we had mid 30's from April to October again and the year before was even hotter (my roof was off for nearly three months).
Attached is a temperature chart of oil, so pick the one you feel is right for the ambient temperature you live in. Personally I like FS oil as it retains its qualities and body unlike mineral oil which seems to turn to ink after a few thousand miles. My old oil is still good and in fact goes into my buddy's old hillclimb/commuter MGBGT.
Cheers,
Steve
Last edited: