my car gradually is decreasing MPG

[Project84]

After reading the thread by "theholycow" about his car gaining MPG (break-in) I've decided to enlist the help of you all to figure out my little Saturn.

First of all, the details.
'96 SL2 1.9L DOHC, auto. typical saturn oil burn issue, meticulously maintained by me (I'm a maintenance man/mechanic) and running 50psi in the upgraded Kumho touring tires. Yes I know, it's not a SOHC 5-speed which is the best candidate for MPG... but I have next to nothing invested in this car.

I used to ALWAYS get 27 mpg.... recently its been a guessing game as to what my MPG will be, but I do check it every single time and my gas log shows each and every fill up w/ nothing left out.

I've replaced the PCV valve, thermostat w/ correct temp rating, fuel filter, upgraded spark plugs w/ OEM gap, upgraded NAPA silicone plug wires, air filter, and tried a snake oil product (Lucas fuel treatment) on the basis of, I swindled my way into a $90 gift card and purchased it because it was basically free to me.

Seems to me that everytime I change something or replace an old part, my MPG decreases/fluctuates.

The coolant is fresh, the engine oil/filter gets changed every 4,000-4,500 miles (although I rarely use the same oil twice, but do generally stick to blends like High Mileage), I rarely/never use A/C, I rarely use all 4 windows (generally just crack the sunroof and a rear window to aid in circulation but reduce drag and wind noise).

The only things I haven't done that I want to do are:
warm air intake
add an addition intake air temp sensor in series to OEM one (resistance, computer reads higher, leaner mixture)
fab a grill block


What gives? Shouldn't I be in the routine 30's by now? I drive the car VERY slowly and it's not often I exceed 60mph on the interstate.

Any help/tips are appreciated.

[yzfdallas]

have you ever changed you o2 sensor, sometimes they will work slow but not give a check engine light. also hot air intakes seem to work well on a saturn.

[Project84]

o2 sensor is OEM/stock as far as I know. I got the car at 125k and it now has 138k 2 years later... I don't drive much.

What really has me itching to give up on this car is the fact that my g/f drives an '04 Grand Prix 3.8L fully loaded and achieves the same/better MPG than my "chick car" Saturn. Grrrr... really gets my blood boiling!

I'm getting more and more interested in giving up on this one and buying another 4 cyl car, but with a manual transmission. I've been hunting for SL1/SC1 cars but with not much luck in finding below 100k mi. and even harder to find w/ 5-sp. I hate thinking of buying an import... I've never done it, and at 23 years old and having owned 9 cars/trucks, that's saying something.

Although, I'm beginning to think 1.8L DOHC 5 speed Integra. Seems in the import world, you can have your cake and eat it too, while with a domestic, your car has to be underpowered and slow to achieve good MPG. Not that I'm worried about being fast, but this 1.9L DOHC is painfully slow, burns oil religiously, and having spend 10 years as a Cleveland, OH car, I've had to replace a lot underneathe it due to rust and premature failure (endlinks, control arms/ball joints, tie rod ends, calipers, rotors, pads..... not due to casual wear/tear, but due to rust and improper function!!! ARGH!!!

[GasSavers_RoadWarrior]

Is the tranny slipping or something? DOHC and auto together aren't the best combo, but sounds like it should be doing better than that. "Very" slowly is sometimes counterproductive with an auto, gotta be fairly brisk so you can get out of the fluid thrashy wasty range, you want midrange acceleration, give it 2500 rpm or so. Also have a suspicion that your valves could be all carboned up, and that your rings are stuck down with carbon...

Personally, I'd do the following if it was my car, i) give it a clean out dose, 8oz isopropyl alcohol, 4oz laquer thinner and 4oz varsol in a full tank of gas, beat the snot out of it every day for a week and feed it a pint of water through the vacuum tubes every time you got it hot. ii) change the tranny fluid and put "Lucas transmission fix" in the refill, (Leave the rest of the snakeoil alone) iii) Refill the oil with 5W30 Valvoline Maxlife (very high detergent stuff) do the following for the change, drain 2 quarts, put in one quart ATF and one quart varsol and run it for 20 mins, drain that, then put the maxlife in it... you might find maxlife smokes like hell for 2 weeks and turns black real quick... let it... after 2 months change to Castrol or Pennzoil high mileage oil, they have less harsh detergent and better seal conditioners, so if it's still a bit seepy and smoky by that time, it should stop with those.

After that I'd maybe change the O2, get NGK or NTK ... but not while all sorts of crap is going to come flying at it while you're cleaning stuff out.

Edit: BTW when you say you "upgraded" spark plugs, what did you use? Not sure if Saturns are Bosch haters or not, they might not be since it was derived from an Opel engine.

[Project84]

IIRC, I used NGK plugs and gapped them per the owner's manual. Plugs were done about 10k mi. ago and then checked, cleaned, regapped about 3 weeks ago.

I don't think the tranny is slipping, although it has always had an odd hesitation going from 3rd to 4th where it sounds (and feels) like it has shifted, RPM's drop about 1000, but then needs another 500 rpm before it'll actually make the big change.

I drive the car just fine, I let it get to 3k before it shifts... if I'm moderately giving it throttle, as if just to "be out on a sunday drive" this is the regular shift point, so I abide by that.

I've heard different stories about adding alcohol and/or acetone to the fuel, as there are plastic components in my fuel line (the entire fuel filter assy. consists of hard plastic lines) and I've hard this isn't a good idea due to that.

Also, a pint of water through the vacuum tube? Are you nuts? That's scary to me....

as some may know, the ECTS on the Saturns are finicky, but mine has been changed several times and I know its working properly.

[Hateful]

From looking at your gas log it just looks like the winter,had one better tank,then put in the snake oil which always reduces MPG until it's ran out.

I don't believe in watering the car either.

[2000mc]

so u have a a dohc, and auto trans... looks like you drive almost all city, cars rated for 21mpg city, and youre looking for 30s...

maybe try taking a leisurely road trip somewhere, see what the car can do on the highway.

[RightontheMarc]

Originally Posted by Project84

while with a domestic, your car has to be underpowered and slow to achieve good MPG.

My Zx2 was faster than nearly every non-modified/non Type R integra, including a few GSRs I had the pleasure of racing back in the day, and at times I have gotten 43+ miles per gallon. My average MPG is also better than all the Acuras. I have gone at least 130 miles an hour in the car with plenty of acceleration left to go. At 84,000 miles I barely burn a drop of oil in 5000 miles oil change intervals with synthetic oil. My finish is glossy and true and I have only ever had to replace the brakes and tierods outer ends because the roads around me are horrendous.

There is a turbo Plymouth Laser on this board that is averaging 40mpg and those m'fs were FAST when they were new. In highschool we always raced a friend of mine's AWD TSI Talon against these kids' 5.0 mustangs and utterly slaughtered them. I wonder if they cancelled the Laser/Talon/TurboEclipses just because the insurance rates got too high or because the cops could not catch them when used as getaways.

The only issue I experience that you might not like that is attributable to being an "American car" is the engine vibrates the stick and steering wheel at idle. It's also kind of loud at WOT. When my muffler finally goes I am going to see if I can get one made for a lexus. Other than that the thing runs like it did at 40,000 miles.

I once had a 97 Escort sedan manual trans as a lease. It had plenty of torque and I would cruise to school sometimes at 110mph back when gas was cheap. It consistently got 36 to 40 miles per gallon long before I ever thought of trying to drive to get better mpg. Oh yeah it was a lot quieter and smoother than my Zx2. It just didn't have the power surge after 4000rpms my Zx2 has. But as far as everyday practical driving it was powered nicely. If you can find one of those in excellent condition with low miles then get it whatever the price is as long as it is not too much higher than blue book. You won't be disappointed with the gas mileage. The a/c also gushed nice and cold.

As far as with your current automatic car, Roadwarrior has the best advice. Brisk acceleration up until you get just above the speed limit then let off the gas to get the tranny to shift into overdrive and try to cruise steady in overdrive with as little braking and allowing downshifting as possible. Anticipate lights, lanes and traffic a half mile in advance. I have also heard of using water (on gm cars at least) to break up carbon deposits. If water makes you squeamish I have heard a stuff called Seafoam works good. Although carbon deposits often increase compression which can improve gas mileage. Get a thorough tranny flush at the dealer. I do all this for my explorer. Even though I rarely drive it I get 19mpg in it compared to the 15 others get.

[Project84]

I have 2 problems with Ford products... #1) that's my day job... to repair Fords. Be it an F700 hi-lift aircraft catering truck, I still know all about Ford's engineering and I'm not pleased w/ it. 2) I routinely make repairs to my friend's g/f's zx2 that has 105k on it and is well taken care of.

I know all about DSM's and I've been searching for one w/ relatively no success in finding one unmolested and/or w/ a 5sp turbo model.... although I owned a '91 Laser 5 sp 1.8L and loved it, those are even harder to find than NA 2.0's or turbo 2.0's.

I have used all the various SeaFoam products with limited success and have written them off as snake oil.

I'm not trying to be so negative, I just really don't know what else there is to do other than fab the warm air intake, block the grill, and pray.

.....so that's my next step. lol

[RightontheMarc]

Originally Posted by Project84

I have 2 problems with Ford products... #1) that's my day job... to repair Fords. Be it an F700 hi-lift aircraft catering truck, I still know all about Ford's engineering and I'm not pleased w/ it. 2) I routinely make repairs to my friend's g/f's zx2 that has 105k on it and is well taken care of.

The only problem I ever had with Fords was where they cut corners on cheap parts to save money and keep the cars cheap. But that has little to do with the actual ford engineering since the parts are made by all kinds of other companies. One example is the flimsy tie rod ends which is the only problem I have had yet in 83k miles. I replaced them myself for $40 each with lifetime warranty. The roads are really potholed and bad around here. Considering the fact that my zx2 was $11,500, is paid off and still looks and runs almost like new that's not a big problem.

Other fords my family has owned all lasted well over 10 years and many over 200,000 miles. They just got too abused, ugly and old to keep by then. Had an abused Festiva once and am now kicking myself for not taking better care of it and keeping it. There is one crackpot on craigslist selling his Festiva for $4800. http://detroit.craigslist.org/car/658799107.html