96' Saturn DOHC 5-spd- where to start
 

Yes, I am new here.
I have looked through many threads, but find few that deal with the DOHC Saturn.

So:
I have a 96' SL2 with the DOHC 5-spd.
178k miles - I run castrol 10w30 with a smoke reducer additive
It used to burn 1 quart/350 miles, now it is 1/3 qt every 350 miles.
I average about 32 MPG in mostly rural driving, most trips 10 minutes or less. I would like to average at least 40 MPG

Looks like the best things to do now are: (not in a particular order)
1. Increase tire psi to about 50.
2. Buy a scangauge /drive & accelerate more slowly + other driving techniques
3. Remove air dam and rear skirts
4. Change the intake resistor
5. Maybe change the 5th gear? -not sure if this is applicable to a 96' or not.
6. Cold air intake?
7. Aftermarket cruise control
8. Some grille blocking
9. Change thermostat?
10. My dad recommended using a water injection with a bottle connected to the intake on a valve - he says it will clean the engine, as well as make the car run more lean.

Any thoughts are appreciated, what I'd really like are guaranteed results.

Welcome.

1. Definitely experiment with increased tire pressure. There's a link in my sig about it if you have any concerns, but you don't sound afraid.

2. Definitely adjust your driving, and tools like the ScanGauge can help a lot.

3. Do not remove your air dam. Many of us are adding air dams or increasing the size of the stock air dam. The only way I'd say to remove it is if it was some funky-shaped ricer air dam that was disturbing the air rather than just pushing it smoothly out of the way. Removing the rear skirts might help.

5. May not apply to you. You say most of your driving is short rural trips; do you spend a lot of time in 5th gear, and if so, how many RPM? Do you feel like you could have a taller 5th gear and still have acceptable power in 5th?

6. Warm air intake. Cold air is for power, warm air is for fuel economy.

7. Will cruise be useful for your short trips?

8 and 9. Worth a try.

4 and 10. I have no clue, maybe someone else can say.

Hey man, I've got an sl1, so I might be able to help you a little bit. I just received my scangauge, and it already is extremely valuable to me. I would def. recommend it. I put my tire pressure up to about 40, and could tell a difference. By air dam, do you mean the little plastic bar that sits behind the bumper? I dont think you would want to remove that, it looks like it would help with aerodynamics rather than hurt them. like holycow stated earlier, warm air intakes are the way to go, along with grill blocking (I really need to do this) and the thermostat change. I believe one of our greatest advantages is the weight of our cars. The plastic side paneling is a great weight saver! Good luck man!

regarding 3. removing the rear lip will help. i go 2-3mpg on my old civic hatch by cutting 3-4 inches off the bottom of the rear bumper going 65mph.

with a car with as many miles as yours has i would do seafoam treatment in the intake manifold and gas tank.

the weakest link on a s-series twin cam is the mp3 transaxle. it has much shorter gearing than the mp2 trans that came in the sohc.

that may be more than you are willing to do, but i felt like putting it out there.

oh and try not to use a/c if you can.

So... how hard do you think it would be to get 40 on average with this car??

I think you can definitely hit 40mpg. I had a 96 Saturn SL2 1.9 DOHC automatic and i'd get 34mpg back in the year 2000. Great car, and it sounds like you keep the oil full (i knew a guy that didn't, and ran synthetic thinking he could run it for 9000 miles no problem. engine busted)

In my Lancer (27/33), I can get 47mpg by going 46mph on the highway...Scangauge can defintely help a lot. I've still got a ways to go to pay for the $160 price, but it helped me not buy a few cars that could have cost me even more.

1. higher pressure is good for mpg, but don't exceed sidewall max
2. scangage is good. watch tps and only give it as much as it needs for the mph you want. shift at 1700 rpm or so. limit speed to 45 or 50 mph.
3. leave the air dam on unless you are building an aero bellypan
4. resistor mod gets overridden by O2 readings. hot air intake is correct solution
5. better 5th would help, but is it worth the cost/effort? taller tires in front would be cheaper. buy LRR tires if you replace them. switch trans lube to full synthetic.
6. idiotic. if you want mpg get hot air, not cold
7. i get better mpg watching tps than on cruise
8. grill blocking was a waste of time/money/effort for 0 gain
9. i have the hotter thermostat, but didn't see any mpg gain from it. in general, hotter is better until it gets so hot it starts retarding spark, IMO.
10. i've also been told water injection would help, but not sure how O2 sensor would react

depending on how frugally you are willing to drive you may or may not get 40 mpg normally out of it, but there is nothing wrong with getting the best you can out of it. it takes the hot air intake 5 or 10 min to warmup, and mpg's don't rise till intake temp does. Maybe you could find a way to rig up a 12vdc heater to heat the intake air immediately after starting the motor.

Please view my HAI build thread in the DIY section... you'll enjoy it and the pics should guide you right through the process. PLAN ON REDUCED POWER if your HAI is actually feeding hot air. Above 130*F intake air temp I can really tell the car has reduced power.

I don't know about 40mpg for an average in city driving, but look at my gas log and see the 43mpg I got on an all highway trip to Cleveland. That tank actually had about 30 miles of city on it too.

I learned by using SGII that accellerating slowly isn't always best. I tend to try to briskly accellerate to obtain the speed limit and then TRY my hardest to stay under 10% TPS to keep that speed.

P&G hasn't shown positive results for me.

Wish I could fix my oil burn issue w/o re-ringing... I'm already collecting parts to do the rebuild. What is this oil additive you're using that cut your oil burn?

Right now I'm using the BarsLeaks additive that is supposed to reduce oil burn.

I'm also considering for the near future doing the top-end clean. (Pouring ATF, kerosene, marvel mystery oil, or something similiar into each cylinder after removing the plugs - there is a thread on it somewhere - its supposed to free up the rings, we will see.)

Did you notice better fuel economy after doing the HAI build? How much improvement?