Higher MPG with thinner oil

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I changed the t-stat on a friend's 96 SL2, for the same reason. It had been 9300 miles since the last oil change, and got all sludged up over the winter from running too cool. It was down about 1 qt. With some fresh PnZ 5w30, after 3000 miles, it was down 2.5 qts, and leaking oil all over the place. But, the soft sludge was gone.

The problem happening now is that it takes forever for fresh oil to flow down to the sump, during an oil change. I think the drain holes in the head are blocked.

Is this happening with you?
A while back I wrote about "better MPG with thicker oil" on my 96 4cyl Saturn DOHC. Now I'm singing a different song.

Replaced the t-stat, as it was reading only around 1/4 most of the time, and did another Auto-Rx treatment (probably didn't need it as the engine is most likely squeaky clean from the previous Auto-Rx treatment about 30K ago and all the LC that's been used, but...)

Filled it up with Pennzoil 5w-20 Synthetic GF-4 after the A-Rx rinse cycle. Even though the bottle is labeled as "SL", it's probably SM if it meets the GF-4 spec, and an M1 filter. I'm wondering if it's PZ Platinum in the bottle??

Average MPG for the 5 tanks post A-Rx rinse is 37.5MPG. This includes a fair amount of A/C and sitting in traffic. I'm simply amazed! No 5-tank range has ever had numbers consistently this high. In the past, if ONLY highway miles were accumulated would this be possible, but now it's happening every tank!!


Too bad I didn't buy the 6 cases of this oil WalMart had for $1.50/qt. I only bought half a case.

[ October 06, 2005, 12:28 PM: Message edited by: ToyotaNSaturn ]
No it's not. The car has 136K on it. It saw it's first Auto-Rx cleaning around 95K, then again at 134K. Lube Control has been used since about 110K. This is probably the cleanest DOHC Saturn engine on the planet!

I do *highly* suggest Auto-Rx, then running LC. It's the cheapest, safest and best way to get these Saturns running truly as good as new.
This topic has me thinking about changing the T-stat on a 168k mile '94 Saturn this weekend. It rarely ever goes above 1/4 on the gauge. If it goes higher, that's usually in summer when the A/C will kick the fan on and cool it back down.

Here's my question: This car requires phosphate-free antifreeze. Is there a readily available OTC brand that will work? (Actually, it's probably full of regular green from a crooked radiator shop that worked on it 2 years ago.)
I verified that the stat was bad by putting both the old and new ones in a pot of water, and turning up the heat. The old one opened up first, while I could still touch the water without getting burned.
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