Garibaldi

2011 GS 19K miles

OK. I need either a dope slap or some education or both.

When I got the recent "If your clutch hydraulic system blows up we'll pay for it until 120k miles or 10 years" notification, it mentioned that you must use "GM approved" clutch fluid. It also states that the problem is caused by incompatible fluid use.

Naturally (don't we all do this?), I went to the manual to check out what was approved. It calls out a GM part number for the US and a different GM part number or Super DOT 4 for Canada.

I rock down to 3 parts stores and all they have is DOT 3/4. WTF?

Is DOT 3/4 compatible with either 3 or 4?

What's the difference and why can't I wrap my head around this?

Thx,

GP

RC4G

DOT 3/4 is actually synthetic DOT4 brake fluid that is fully compatible with brake systems that may be currently using DOT3.

I use Prestone DOT4.

Gearhead Jim

I'm not sure about the synthetic part, but DOT3 and 4 are supposed to be mixable. 4 just starts out with a higher boiling point, the boiling point of either one will decrease as it gradually absorbs moisture from the air.

I'm guessing that the stuff labeled DOT3/4 is so people whose owner manual says to use DOT3, will understand they can use the other stuff also.

There are some fluids labeled DOT3 that actually meet the DOT4 specs. Either way, you might have to prove to GM that you've been using DOT4, so save your receipts and shop bills.

John Harry

For what it's worth, all brake fluids are synthetic.

Garibaldi

Okeedokee, Folks,

I've been educated. I appreciate the feedback.

Thx,
GP

Neil Baker

I disagree with the same same for DOT 3 and DOT 4. They are different. My car, 2008, calls for DOT 3 BRAKE fluid. DOT 4 CLUTCH fluid. They are different!!!

Gearhead Jim

Well, they are somewhat different in their chemical mix and boiling points. But they can, and have been for decades, interchanged and/or mixed.

For normal street driving, DOT3 works fine for most brake systems, including the C6. It's also easier to find and, if you only flush the fluid every 10 years like most people, might actually be a bit better after long usage. So most makers specify DOT3.

IIRC, clutch fluid gets exposed to higher temperature than most brake fluid, so it's common to specify DOT4 for the clutch.

If there was a problem with using DOT4 brake fluid in the C6, there would be lots of Corvettes in the ditch with brake problems. I don't track our car but do sometimes drive hard in the mountains, the dealer has been using DOT4 in my brakes (I also flush each year) since 2001.

Neil Baker

I think you missed the point...C6 calls for DOT 4 in the clutch, some people have been using DOT 3!

gbrtng

Um ... I guess silicone fluid is "synthetic" too, but you don't use it in any GM application I know of. Silicone fluid is apparently used in some motorcycles.

GMJim

GM letter?? Are you in Canada or the States? I have a 2011 ZR1 but no letter........yet. Btw I've been using GM p/n 88901244 Super Dot 4.

Garibaldi

I'm in the States.