Just picked up a unmolested 1998 5 speed a couple weeks ago and am guinea pigging it to see what can be done to extract more gas mileage. Here’s the plan…
I have chosen a Mobil station and 90 mile freeway driving loop for this adventure, and have become quite proficient at filling up the gas tank until the gas is visible in the filler neck so i know exactly how much has been used.
I have limited my driving style to shifting at 3000 rpm and keeping the speed at 70mph, give or take 4mph either way (it’s not flat country out here and the car has no cruise control lol)
So far I’m five trips into this venture and have brought fuel economy from a 34.24mpg to 37.5mpg.
So far here’s the breakdown of the first 5 sets of mods…
Run 1: Car is as purchased, with 10w30 wal mart oil and fram oil filter, and almost new Goodyear Integrity tires on the base model steelies. Tire pressures were 30lbs, front and rear, and the trunk and passenger compartment were free of any additional weight items… I consumed 2.64 gallons. and ran the car at dusk, turning the headlights on about halfway thru the trip
Run 2: Weight removal bits… I removed the spare tire, jack, false floor, and carpet pad from the trunk. Under the hood I removed the motor mount dampers and engine lift hook, and inside the car i removed the steel sandwich plate inside the glovebox… about 50 lbs total. I also upped the air pressure to 38lbs in the front and 34 lbs in the rear. Headlights were on the whole time. Consumption was 2.58 gallons (34.88 mpg).
Run 3: Added 14x6 motegi alloys, installed lowering springs in the rear only to improve stance (sits level looking now instead of that Dodge Neon kicked in the ass look of the stock springs), and installed a zxtuner ultra udp while replacing a noisy idler bearing. Headlights were on and consumption was down… 2.44 gallons (36.88 mpg)
Run 4: Switched out oil to 0w30 Mobil 1 and a motorcraft oil filter, added a 170 degree thermostat, reset the pcm, and removed the lower resonator from the stock intake. I drove the car for about a week to get the pcm to start learning its parameters again. Headlights were on and now I saw 2.40 gallons used (37.5mpg)
Run 5: I added a hi flow elbow to the TB end of the stock intake and ran again… Hot day, no headlights, and 2.41 gallons used (37.3 mpg).
As for how the car runs, it’s a tad smoother than stock, with a noticeable boost in power (the 'ol butt dyno says about 10hp).
I have a few more plans for the mpg upgrades, and if any of you out there have any ideas or suggestions on what to do to increase mpg, i’m all ears.