C-4 oil & coolant

[Glen C.]

Wanted to get some opinions on the oil and antifreeze to use in my (new to Me) C-4 with a L98 engine. The owners manual calls for API SF/CC or SF/CD. I was going to use CJ-4 oil that I use in my two C2 Vettes. Regarding the coolant, I use Prestone DEXCOOL antifreeze in my 66 BB & Zerex G05 in my 64 SB. Any problem with any of these decisions?

[Lyndon S.]

Re: C-4 oil & coolant

I use Mobil 1 in my L-98 because that is what the first owner ran. I use the zerex in it also.

[Duke W.]

Re: C-4 oil & coolant

You can see that those owners' manual recommended oils are dual-rated. They met the then current S and C-categories, and most oils at that time did, so you could use the same oil in an auto engine or a HD diesel engine.

Even if your C4 has a roller cam, the rockers are likely slidding surface, so I would use current CJ-4. If it's a flat tappet cam, definitely use CJ-4.

The best anti-freeze for any vintage cooling system with soldered components is G-05. There is some issue with "lead leeching" by Dexcool that could potentially affect solder joints. I wouldn't necessarily change the anti-freeze in your '66 tomorrow, but when it's due for a change, use G-05.

If your C4 calls for Dexcool you can use it, but some don't like Dexcool, so G-05 should be okay. If it's pre-Dexcool use G-05.

Duke

[Glen C.]

Re: C-4 oil & coolant

I used Mobil 1 years ago in my 1974 SD 455 Formula. In those days the API rating was only SC or SD. Long story short, my cam shaft was wiped out. Some would say it was due to not enough ZDDP. Maybe Mobil 1 will work OK in a L98, but I don't think there is any difference in the valve trains?

[Glen C.]

Re: C-4 oil & coolant

The L98 is stock, so as far as I know, there are a lot of flat tappet sliding surfaces in that engine. I just wanted to check. I know the answer on C-2's is API CJ-4!
My 66 BB has a Dewitt Direct Fit all aluminum radiator, not the original copper brass unit, but the heater core could still be a problem. I'll go with the G05 next coolant change on my 66.
Regarding the C-4, it is an 86. I'm pretty sure that it is before DexCool was around. The owners manual says use an ethylene glycol antifreeze meeting GM Specification 1825-M. Not sure what that means, but suspect it has something to do with the aluminum radiator and other components.

[Duke W.]

Re: C-4 oil & coolant

1825-M is the pre-Dexcool spec, so use G-05, which meets 1825-M. Dexcool doesn't. IIRC Dexcool was standard fill on all GM vehicles except Saturn beginning in 1996. Saturn followed a year or two later.

SC SD probably had about the same amount of ZDDP as current CJ-4, but the SD455 likely has much higher rate valve springs and higher unit loading on the valve train sliding surfaces than any OE Chevrolet small block.

I know the Pontiac OHC-I6 had a lobe wear problem that the engineers never figured out. I've never been aware that Pontiac V-8s had an issue, but I recall the SD455 has very aggressive lobe dynamics - even more so than the mechanical lifter lobes from the sixties - so apparently they found the limit.

Duke

[Lyndon S.]

Re: C-4 oil & coolant

So should I change out the oil in the 89 corvette to Mobil delvac , I use it in the 71 with L-S 5.?

[Joe L.]

Re: C-4 oil & coolant

The L98 is stock, so as far as I know, there are a lot of flat tappet sliding surfaces in that engine. I just wanted to check. I know the answer on C-2's is API CJ-4!
My 66 BB has a Dewitt Direct Fit all aluminum radiator, not the original copper brass unit, but the heater core could still be a problem. I'll go with the G05 next coolant change on my 66.
Regarding the C-4, it is an 86. I'm pretty sure that it is before DexCool was around. The owners manual says use an ethylene glycol antifreeze meeting GM Specification 1825-M. Not sure what that means, but suspect it has something to do with the aluminum radiator and other components.

Glen------

You mention an L-98 but, unless I missed something, I don't see that you mentioned what year. It makes a difference. The L98 was installed from 1985 thru 1991. However, the 1985-86 used a flat tappet cam while the 1987-91 used a roller cam. If you have a 1985-86 you definitely want to use the CJ-4. If you have a 1987-91, you could use the current S-rated oil or you could use the CJ-4. If it were me, with the 87-91 I'd use the current S-rated oil.

ALL C4 Corvettes use aluminum radiators but with a copper/brass heater core. So, I recommend the use of Zerex G-05 for all (even the 1996 which required Dexcool).

[Joe L.]

Re: C-4 oil & coolant

So should I change out the oil in the 89 corvette to Mobil delvac , I use it in the 71 with L-S 5.?

Lyndon-----

For the 1989, I'd recommend that you stay with the current S-rated oil.

[Glen C.]

Re: C-4 oil & coolant

When I had the SD "freshened up" a few years ago. Because the SD cam was unique, I had a choice to either regrind the old cam or go with rollers through out the valve train. I chose the latter. Previously, I had broken the top off of a rocker arm stud, so it was time to make a change. Thanks for your input.

[Glen C.]

Re: C-4 oil & coolant

Joe, What are the reasons for that recommendation? Would you also say that for an 86?

[Joe L.]

Re: C-4 oil & coolant

Joe, What are the reasons for that recommendation? Would you also say that for an 86?

Glen-----


For a 1986 I'd use the CJ-4 diesel oil (which is also current S-rated for gasoline service). For flat tappet cams you want the zinc and phosphorous that oil provides. For roller cam engines, I don't think it's necessary and I prefer the overall attributes of current S-rated oils.

[Jim T.]

Re: C-4 oil & coolant

Joe I have had my 1985 since 1992. When I read about the benefits of using CJ-4 from Duke I switched to that type of oil for the 85. When I changed anti-freeze the second time in the 85 I used Dex-Cool because my 1996 LT-4 came with it. Just this year changed the 85's coolant and refilled with Zerex G-05. Also changed my 1968 to Zerex G-05, I have been using CJ-4 in its 45 year old engine as well. After reading Joe L.'s above post I now think I will change from Dex-Cool in my 1996 LT-4 to Zerex G-05.

[Glen C.]

Re: C-4 oil & coolant

You are correct I did not mention the year (86) until my third post, Thanks for the clarification on the flat tappet vs: roller cam, I wasn't aware there was a valve train change in the L98. That said, I'll be using the CJ-4. & G-05 for all three of my Vettes. Thanks!

[Joe L.]

Re: C-4 oil & coolant

Joe I have had my 1985 since 1992. When I read about the benefits of using CJ-4 from Duke I switched to that type of oil for the 85. When I changed anti-freeze the second time in the 85 I used Dex-Cool because my 1996 LT-4 came with it. Just this year changed the 85's coolant and refilled with Zerex G-05. Also changed my 1968 to Zerex G-05, I have been using CJ-4 in its 45 year old engine as well. After reading Joe L.'s above post I now think I will change from Dex-Cool in my 1996 LT-4 to Zerex G-05.

Jim------


By 1996 when GM basically went to the Dexcool requirement "across the board", most GM cars and trucks had been changed to aluminum radiators AND aluminum heater cores. Corvette was an exception. At the very end of the C4 era, it still used a copper/brass heater core. For a C4 Corvette, heater core preservation is of paramount importance, so I recommend the coolant that is easiest on copper/brass heater cores and their solder joints. That coolant is Zerex G-05. It's not vastly superior to the other coolants in this regard but, as I say, for C4 Corvettes, heater core preservation is of paramount importance.

Normally, I take GM's automotive fluid recommendations very seriously. 1996 Corvettes are an exception. I think GM "blew it" on the Dexcool recommendation for 1996. The cooling system for 1996 Corvettes was not substantially changed from that used for 1992-95 Corvettes which required coolant meeting GM's 1825-M coolant spec. 1996 should have required the same spec (which Dexcool does not meet). Zerex G-05 meets the 1825-M spec and is also the best choice of all 1825-M spec coolants for a car with a copper/brass heater core.

By the way, I'll be soon presenting some information which will change my coolant recommendations in certain cases as a result of some new developments.