Thread: Good evening. New here, a few quick questions..

So i just got an '04 GP GTP. I previously had '98 Buick Riviera which had effectively the same drivetrain with the series II SuperCharged 3800.
I put a 180° T-stat in it (the Riv) and opened up the baffling in the airbox to let it breathe better and let the whine out, drove it for 85,000 miles of regular full throttle romps, and sold it for half of what i bought it for.. but i loved that car.

So i figured I'd find another Supercharged 3800 and I did.

Is there any known issue with installing a 180° t-stat in these?
on the Riv it would throw a low coolant warning since the low temp of the coolant confused the computer.

Someone did a resonator delete mod on this car which is fine, it sounds good at idle but a bit ratty when stomping on it, but whatever, its all good.

For the record, I was doing 10-12K oil changes with Mobil 1 15w-50 (Red Cap)* and Purolator Pure One filters, and it was still running like a top at 205,000 when i sold it, and i plan to do the same intervals on this engine, though with somewhat lighter oil.
I found a Wix cross reference page and did a screen capture, but i don't know what I have for clearance, or more properly, what is the largest dimension diameter and length that will without hitting things..

I would like to find a cross ref for a slightly longer and fatter filter (more media surface area) that will fit without issues if anyone has that info kicking around..

So anyway, Thats my bit.


*(yes, i know that is ridiculously heavy oil relative to spec, but i had a remote car starter and gave it 5 minutes of warm up before i even got in the car every day)

Originally Posted by Fivefingerdeathpunch

A stock thermostat is just fine, there is no need for a 180 thermostat. You are not gaining anything by having the engine run cooler and in fact if you want to get technical it could perform worse when the cylinder temps are less. If engines could run at 250 degrees and not melt other system down and have no other issue it would be more efficient. But that's not really ever going to happen.

So the stock 195 degree thermostat is just fine. Me personally I've jumped over the LS game for several years now and stock thermostat's are still the best option even on cars making 400-800hp and the only time people want something cooler is if they track the car.


The wix 1040 is the short filter and the 1036 is the longer filter. There is no fat filter that I know of. Though I'm sure something would screw on with the same thread pitch but sealing correctly on the oil filter housing is another story.

Anything longer than the 1036 will fit the subframe or lower control arm.

Probably go with a 5W40 or similar. Give the bearings a break in the winter with the 5W rating.

Thanks for your input, I appreciate the consult.

Out of curiosity, why would higher coolant temperature increase efficiency?
Seems counter intuitive given the trend toward ceramic coating of piston crowns and combustion chambers, acting in an insulative manner, reducing pre ignition by minimizing hot spots.
Personally, i like having some thermal headroom between t-stat wide open and risk of boilover.
I was mostly wondering if others do this and if they end up with warning lights or CEL going on because of it.

Thanks for the filter info too, the Wix 51036 cross references back to the Purolator Boss PBL24011, so i have a couple of those on order.
I used 5W-30 when i did my first oil change on the car yesterday, but we still have snow on the ground here and another month of cold weather before the sun comes back, and no remote starter on this one..
so yeah i will have to be more conservative on the viscosity on this one for a while

heavier oil is really not a problem for startup oiling, (especially when running a fully synthetic since they flow so much better than Dino juice, especially cold..)
but it does require warm up time to flow well enough for driving, and without the remote starter, i don't want to romp on it too quickly and hurt the motor