Hello there!
I'm the happy owner of a 1986 C4 with L98 (cast iron), flat tappet cam, 79k miles and is running fine afaik. I have to change the oil but i'm very doubtful on what should i go for.
I live in Italy so it's not easy for me to get access to spare parts. hence i would like to maximize as much as possible the good state of its engine, starting by putting the right oil. The engine is not stock but modifications should be very light (maybe 10 hp more than stock). I use it for few hundreds miles per year with no racing, just some pulls from time to time.
I know the previous owners run a blend MOTUL 15W40 and a blend 10W40 SN/CF, with the latter currently filled in.
Beside knowing that i should put the oil recommended by the car manual, i know little about this topic. I read many threads on the forums but i'm unable to get to the final point of which one i should go for.
From what i understood i have to look for an oil which has a good amount of ZDDP, saying between 1000 and 1400 PPM. SM and later are no good due ZDDP level around 600. I'm having a very hard time finding any Zinc additive in EU such as HY-PERLUBE ZINC REPLACEMENT, but I instead found the MOTUL CLASSIC NINETIES 10W-30 (spec sheet attached), which is reported to have ZDDP at 1800 PPM, but seems to be too much (btw the MOTUL oil selector tool suggest me this one).
I would like to kindly ask you what do you suggest, and if the MOTUL CLASSIC NINETIES 10W-30 could be a viable solution when mixed with another oil (which one?) to lower the ZDDP levels around 1300-1400 PPM.
Also, can i go for a sythetic oil with cleaning features, or should i stick with blend to avoid engine oil leaking?
On a side note i read about a forum user always using Castrol GTX on its 85 C4 with heavy mods, and racing it hard with no issues after 100k miles, so I could be just overthinking about the oil decision.
Thank you!
I'm the happy owner of a 1986 C4 with L98 (cast iron), flat tappet cam, 79k miles and is running fine afaik. I have to change the oil but i'm very doubtful on what should i go for.
I live in Italy so it's not easy for me to get access to spare parts. hence i would like to maximize as much as possible the good state of its engine, starting by putting the right oil. The engine is not stock but modifications should be very light (maybe 10 hp more than stock). I use it for few hundreds miles per year with no racing, just some pulls from time to time.
I know the previous owners run a blend MOTUL 15W40 and a blend 10W40 SN/CF, with the latter currently filled in.
Beside knowing that i should put the oil recommended by the car manual, i know little about this topic. I read many threads on the forums but i'm unable to get to the final point of which one i should go for.
From what i understood i have to look for an oil which has a good amount of ZDDP, saying between 1000 and 1400 PPM. SM and later are no good due ZDDP level around 600. I'm having a very hard time finding any Zinc additive in EU such as HY-PERLUBE ZINC REPLACEMENT, but I instead found the MOTUL CLASSIC NINETIES 10W-30 (spec sheet attached), which is reported to have ZDDP at 1800 PPM, but seems to be too much (btw the MOTUL oil selector tool suggest me this one).
I would like to kindly ask you what do you suggest, and if the MOTUL CLASSIC NINETIES 10W-30 could be a viable solution when mixed with another oil (which one?) to lower the ZDDP levels around 1300-1400 PPM.
Also, can i go for a sythetic oil with cleaning features, or should i stick with blend to avoid engine oil leaking?
On a side note i read about a forum user always using Castrol GTX on its 85 C4 with heavy mods, and racing it hard with no issues after 100k miles, so I could be just overthinking about the oil decision.
Thank you!
Attachments
Last edited: