Clutch replaced, increased fuel economy

I drive a 1997 Saturn SC2, 5-speed (she will be 15-years old in September). She got 126,000 miles on the original clutch - down to the rivets, before it had to be replaced. There are now 138,361 miles on her. But, after replacement, the fuel economy became so much better - city 29 mpg vs.26 mpg; partial tank highway 37.7 mpg vs. 32-33. Does anyone have any idea why this would happen? I have asked the dealership, and no one seems to know the answer. I always use top tier fuel - not the no-name garbage. BTW, I am not complaining!
And, the clutch is adjusted at the top of the throw, making it extremely difficult to use. Is there anything that can be done - now that it’s out of warranty?

If you’re measuring the fuel economy correctly (fill/drive/fill & divide miles driven by gallons to refill over many tanks of fuel) then it makes perfect sense if your old clutch was slipping. The slipping means lots of engine work without locomotion. A lot of your old fuel basically just went to heating up the old clutch.

As for adjustment, I’d start by just bringing it back to whomever did it & tell them what is going on.

A couple of things come to mind. I doubt it is the clutch replacement itself that has improved your mileage, but, to get to the clutch, the transmission is dropped. I would never drop a transmission without draining the gear lube. And, I’d never put the drained lube back in. I suspect the new, fresh gear lube is party responsible for your mileage gains. Did you ever have the gear lube changed in these last 15 years? It is an often overlooked maintenance item. I generally use a 60,000 mile change interval for my stick-shifts, even with the synthetic gear lubes available today.

The battery is also disconnected, and this resets the computer to basic defaults. Resetting the fuel trims and ignition adjustments may be making up the rest of the difference.

If your clutch was slipping, even a little bit, that’s energy that wasn’t getting from the engine to the rear wheels. With a new clutch, all that wasted energy is now being put to use, increasing efficiency and gas mileage.

I have pulled the r/o for clutch replacement. Work done: R&R clutch disc, R&R pressure plate, R&R throw-out bearing, R&R rear main seal assembly, resurface flywheel. I provided transmission fluid. For this car, the transmission fluid is replaced once - at 6,000 miles - never after that (except for repair).
I have been told that to open the gear case (the large, round, silver thing with large bolts through the edges??) is very expensive - as it is, family helped with repair. So, no, the gear lube has never been changed - unless BustedKnuckles is talking about something else.
As for the clutch slipping - it slipped exactly 3 times, and that was after I was told the clutch needed replacing. And, I measure mileage exactly as does cigroller.
I’m not aware that any of the basic defaults have ever been changed. This baby goes to the dealership - not chain stores or private shops. I learned by going to a chain for a tune-up, providing the owner’s manual open to the page for spark plugs and wrong plugs being installed and having all the associated problems. My money was refunded. This was a Firestone dealer, and they couldn’t even rotate tires correctly, again - with the owner’s manual open to the page on rotating tires. Two guys, each holding a tire, and chasing each other around the car - what a hoot!

Maybe they re-inflated or over-inflated your tires?
Ask them to adjust the clutch release so it engages lower.

In the future, no need to take an out of warranty car to the dealership for routine work.
A good independent, non-chain shop can usually do the work for less.

Wait a while and you will get used to the clutch. It’s new and it might change a little but I don’t really know if it will happen fast enough for you. I hate some of the clutches I’ve tried over the years. It’s difficult getting used to a different one in a week.


Don’t buy into that ‘lifetime’ fluid hype. It is just that, hype. VW has claimed for nearly a decade that their transmissions have a ‘lifetime’ fluid, but ZF, the people that make the transmissions for VW, have said in writing that they are incorrect. ZF recommends at least a 60,000 mile transmission fluid change for almost all of their models.

Manual transmissions have no filter, so any shavings and metal particles from wear are suspended in the fluid. Enough can accumulate to reduce the lubricant’s properties and accelerate wear, just like engine oil. The only way to get it out is to change the fluid periodically.

I’ll bet that you probably felt the shifter move around a little bit easier after the change-over. This is due to fresh fluid.

The saturn uses ATF in the manual transmission, not gear lube. It does last a lifetime, I have over 235k on mine. You can change it if you want to, but its a waste of time and money.

Actually, Busted Knuckles, the shifter moved more easily because one of the symptoms of a vehicle needing clutch replacement is that the shifter won’t go into certain gears - mine was 1st & 3rd.
pleasedodgevan2 - the clutch was replaced over a year ago - over 12,000 miles ago. So, no, I have not gotten used to it. I can grind it along with the worst of 'em.
circuitsmith - I have yet to follow the link you provided to Car Talk - don’t you just love that program? I’ll get to it, though. Because of my financial situation, the plant manager at the former Saturn dealership helps me out with the bills. And, truthfully, there is absolutely no one out there (especially in K-town TN) that I would trust. I know, and trust, the plant manager. When I’ve had the car in and he wasn’t there that particular day, everything that could go wrong, did. When Saturn went out of business, they sent me a card for 4 free O&F changes with tire rotation for being such a good customer. I get the tires balanced each time and ask that they put 30# in each tire. But, I will check the link.
So, it seems there may not even be a logical reason. I’m just really happy that I can go lots farther on a tank of gas - it helps, because I do lots of hiking in cool weather and drive at least 200 miles round trip for each one. Thanks, guys.

I still think that you’re likely to have had some excess slipping before you knew it was slipping. You said it slipped 3 times - those were the times you knew it was slipping. Slipping is a matter of degree. In fact, the clutch slips every single time you let off of it - that’s its job. So it can be slipping more than it should long before it feels like classic slipping.

Perhaps, somehow, 90 weight gear oil came out and the correct ATF went in…

OR,…Half the original ATF leaked or drained out when the transmission was removed and was not replaced. This might reduce drag a little, but not enough to account for the figures you quoted…

Maybe your friend the plant manager had some extra maintenance done without bothering to put it on the ticket or even mention it to you.
Like replace a sticky thermostat, clean the MAF sensor or even put in a fresh O2 sensor.

“Actually, Busted Knuckles, the shifter moved more easily because one of the symptoms of a vehicle needing clutch replacement is that the shifter won’t go into certain gears - mine was 1st & 3rd.”

Hard to shift may be a symptom of trouble with the clutch release system, not the clutch itself. I’ve worked on stick-shift cars for 20 years. Even with a completely worn out clutch slipping like crazy, the shifter should have been smooth and crisp if nothing else was wrong. If the only other difference was fresh gear lube, that may be the smoking gun that old, contaminated fluid was at least partly responsible for the shifting and mileage issues you noticed. You’d be surprised the difference a good, fresh lubricant in the drivetrain can make.