Hey Guys,

Can you please let me know what are the best products to use for the following:

• Coolant (planning a full flush)
• Diff (planning on a full flush)

I just want to know what to ask my mechanic to use (if one is better than another)... I have an 02 (if that matters).

Thanks!

 

- Your C5 originally comes with GM Dex-Cool, so if you are planning a coolant system flush it would be ideal to fill with Dex-Cool.

- The rear differential utilizes a 75w-90 fluid that GM has a replacement product for. Many individuals utilize a product like RedLine, AMSOIL, or similar. There is a driving procedure upon rear differential fluid replacement that you should follow. It includes;
- No wide open throttle for approximately 300 miles
- Immediately after fluid change, proceed to an open area (like a parking lot) and perform multiple turns (such as 'figure 8s') to ensure that differential fluid lubricates internal mechanisms.

 

From what I've read. Any diff fluid that has limited slip additive, you can skip the "break in" procedure. No time needed for additive to work itself into the fluid like GM fluids need. Either way, I promptly ripped it down the street after Redline diff fluid. No problems to report.

 

Peak Global is a modern, improved version of Dexcool. It is what I use.

 

One other question...

My 02 has only 55k miles... Do you flush the coolant and Diff based on number of years or mileage?

I was thinking that the car is now 15 years old and that a full flush of both would be a good thing...unless Im told differently.

Thanks!

 

I use Dex-Cool in my car and the owner's manual says change the coolant every 5 years or 100K miles, whichever comes first.

 

The recommendation for the cooling system is a coolant flush and refill every 5 years using Dex Cool.

I looked in the Owner's Manual for info regarding the diff for my '02 and it shows using a SAE 75W-90 synthetic fluid and 1 bottle (4 ounces) of the GM Limited Slip additive. I did not find any specific schedule (time or mileage) for changing the fluid. It says to just check the fluid level twice a year and top off as necessary. Couldn't hurt to change it now, but it's not a big deal as long as the diff is working properly and there is no noise or chatter from the clutches.

 

Coolant is only good for about 3 years regardless of mileage.
Coolant touches everything. Don't cheap out.
Not just radiator, but heads, block, htr core, wtr pump, head gaskets,
etc etc
I've never figured out why people pay so much for (any) car and
don't just do preventative maintenance.
Differential I'd replace every 5 years at least. This helps
prevent leaky seals, etc in the rear end. It's pretty cheap and easy
to do. Same for trans fluid (if M6). Auto A4 I change every other year (unless mileage comes first - 20k)

 

Modern coolant formulas are good for longer than three years. You can easily get 5 to 8 years. Two years on tranny fluid? That's overkill. If it makes you feel better then go for it, but it is not necessary.
Pay so much? I paid $16K for my used car.

 

I'm the original owner of my '01, and for me, Dex-Cool in the cooling system, changed every 4 years. In the rear end, I changed the gear oil annually, for the first 3 years. That got the grey, grimy looking moly lube that GM initially sets up it's diffs with, out of the diff. after that, 13 years, I believe I've changed it one more time. But since it's now quite clean, and I don't put more than a couple thousand miles a year on it, I'm not in a hurry to change it again.

 

For the coolant, 5 years/100K miles for Dexcool (the factory fill).

For replacement, I prefer one of the "universal long life/universal extended life" coolants. You can buy that in name brands (Prestone or Zerex), or in "house brands" (Napa, CarQuest, O'Reilly).

Dexcool is OK, and "on paper" it's a better coolant. If anyone mixes it with the wrong stuff, or if any air gets in the system (leaking heater core anyone), the results with DexCool are generally catastrophic. The stuff turns to sludgy mud when mixed with air or with older conventional "green coolant." The "universal" coolants mix with anything with no ill effects, and have fewer issues with even air in the system. Don't run DexCool or any long life coolant much past 5 years either. Initially, DexCool was specified as a 10 year/100K mile coolant, IIRC. It's definitely not something you want to push to 10 years.

The moaner's annual is pretty silent on the differential on these cars. My general recommendation is one change early (7,500 to 15,000 miles or one year), and about every 3 to 4 years or 45,000 to 50,000 miles after that. That's in line with most RWD/4WD trucks and SUV's which use similar diffs. I do the same intervals for manual gearboxes.

Automatic transmissions I try to do a filter and fluid change every 30,000 miles (or every 3 years, whichever comes first) for most of those, but if it's past 75,000 miles, I just let it ride with "lifetime fluid." Disturbing the fluid in an older automatic transmission that's never had a fluid change is bad luck in my experience. You'll be rebuilding it sooner if you change it at 75K or 90K or whatever than if you just let it go and believe the claims of "lifetime fluid."

You've got some pretty good recommendations for the diff lube here. Any lube that meets the specs in the owner's manual/service manual, with the GM limited slip additive.

 

Coolant: https://prestone.com/products?detail=AF888

Diff: http://www.toquez06.com/diff.html

 

Dexcool in the radiator and Redline (with slip) 75w-90 in the differential.

 

I've had mine since new in 2000. I read lots about people having cooling issues, trans issues,, etc etc
In 2000, Dexron III was the fluid. It's NOT synthetic. And if you
want to go along time w/o trans service, that's your choice. But if
you don't want to have to tear into the 4l60e for a long time, then
preventative maint is where its at.
I've never had to replace my water pump, etc either..
I'm Pushing 120K miles. Runs just as good as the day I drove it home in May 2000.
I also change my oil minimum of 2 times per year. Even if I only get
a couple thousand miles on it a year now. it's really cheap . Easy to do.
And gives me peace of mind. I pulled my valvecovers off just to check
out springs/ rockers. They were cleaner on the inside than on the outside.

 

Like I said if it makes you feel better, go for it. But it is overkill. When I bought mine the tranny fluid and coolant had not been changed for 12 years. I changed them and both were still like new. Checked acidity of coolant and it was fine. Put 30K more miles on it and it runs like new and shifts perfectly. Absolutely no problems. Factory recommended scheduled maintanance is 50K miles for tranny fluid and 150K miles or 5 years for coolant. Now if you are hard on your car and abuse it then it should be sooner.

 

DexCool

GM # 88862624 LS Gear Oil (has anti-slip additive)

 

I would use water from a mudhole before I would put Dex-cool in my car. I have seen many, many, many early failures (usually heater core) with Dex-cool. I lean towards Prestone myself though I will use Peak in a pinch and always with distilled water.

 

Peak Global is the best there is. Prestone is mediocre.

 

Interesting.............

I owned a 1996 Z/28 Camaro for 19 years, as well as a 2005 GMC Canyon for 10 years, along with my 2001 Corvette for 16 years. The common denominator......Dex-Cool coolant in ALL of them from day one, flushed every 4 years, with ZERO issues.

 

This:
This is the big problem with "long Life Coolants".. People don't change them. Any long life universal is really fine. AS Long As You Maintain !
I saw plenty of dexcool issues in my day.. It's not "bad" coolant.
You just cant mix anything else into it (why would you)
And Change it regularly . Just like any OE coolant.. It all goes to
**** in time and causes issues. Our cars are now OLD.. Just because you
only put on a couple thousand a year, doesn't mean its good for 100K miles.