FAQ: Improving Bad Gas Mileage

Hey guys, I'm wondering if there is a problem with my car or just common riviera gas milage. I get roughly 550 KM to a full tank of premium gas which seems a little low to me. Is this the case or do these cars normally get that milage? What can contribute to this poor milage? My air filter is fine, I'm not sure about my plugs (never changed them), tires are inflated fully..... I'm just not sure what to look for. Thanks! (BTW: 1996 S/C -- No Mods)

I don't know what that comes out to in miles but I was getting about 300 miles per tank and I was getting like 16 mpg.

I changed out the plugs and wires and it went up a little but NEVER went over 18.

I recently clean out the engine top end/fuel system with seafoam and my mileage is up over 20 the last 2 weeks. I also installed a FWI right after the seafoam so I don't know if its the intake or the seafoam (or both) that helped out.

I would change the plugs and look into the seafoam cleaning. Maybe gut your airbox and get a k&n drop in if you don't want to do the FWI or CAI.

I'm a freak for the cruise control. I don't know if it's just in my head but I seem to get a ton of miles out of her with little fuel used.

I with I had a fuel consuption meter like Regals have.

I could go for some more air in my tires

I've checked the Riv when my parents were driving it at 26+ multiple times. The lowest it ever did was 24, and highest was 27.

550km on a tank doesn't tell us enough. How many gallons did it take to refill from running those 550km? When my gauge shows empty, I can still only get about 15.5 gallons on a fill, nowhere close to the approx 18 gallons it should hold. My city/hwy mix of driving gets me around 21mpg average. I would do better, but for some reason my Riv likes to accelerate quickly from a stop... For hwy mileage, you should be doing at least mid-20's if not better, with a properly tuned and maintained car. Replace the air filter, a K&N is a good choice unless you want to stick with OEM. Never replaced plugs, or inspected them? Time for new plugs, probably could use a new fuel filter too. Seafoam or GM top engine cleaner can help too.

Phoenix wrote:

Hey guys, I'm wondering if there is a problem with my car or just common riviera gas milage. I get roughly 550 KM to a full tank of premium gas .............

That's about 342 miles. Not unusual mileage, if you're talking a mix of city/hwy. Remember these cars were rated at like 19/26 when new.

depending on city vs. highway driving, about 300-350 per tank is right when I do mainly city driving, probably 70%+.
on the highway only I can get about 450+ on the tank.

Thanks for the replies guys! I'm going to look into that seafoam cleaning and change out my plugs as soon as I get some extra money I'll post with an update whenever that happens lol.......

Just averaged 20mpg last tank in mixed driving in 90 degree temps with the A/C on half of the time. Stock plugs, gutted air intake.

You guys shouldn't feel bad about those numbers. I've been driving a 4 cyl Mazda for a week, averaging 24 mpg so far. This is mostly freeway driving. Considering how much quicker and heavier the Riviera is... i'm not impressed with this "economy car". i can get just over 300 miles out of its 14.5 gallon tank.

Seafoam and plugs will only be like $10...go for it.

AA wrote:

You guys shouldn't feel bad about those numbers. I've been driving a 4 cyl Mazda for a week, averaging 24 mpg so far. This is mostly freeway driving. Considering how much quicker and heavier the Riviera is... i'm not impressed with this "economy car". i can get just over 300 miles out of its 14.5 gallon tank.

thats cause you gotta drive it redline to redline to get anywhere.

So true. I just drove it 250 miles on the freeway to visit the mom today. Got about 26 mpg this time. Woo-whooo!

ok...so im gettin unsatisfactory gas mileage...not exactly sure y...but i was gonna try an octance booster(i use 93 premium gas at all times as it is, mostly shell), a gas treatment, and a fuel injector/carburator(sp) cleaner. i know i saw a write up for the hand cleanin fuel injector so no need to send me a link for that. just wanted to know if any of u guys use these things and notice any lil bit of difference in gas mileage.

Don't waste money on any octane booster. I occassionally run fuel injector cleaner, or Seafoam thru the fuel system. I don't see noticeable changes, it's just preventive maint.

1998 Riv wrote:

Don't waste money on any octane booster. I occassionally run fuel injector cleaner, or Seafoam thru the fuel system. I don't see noticeable changes, it's just preventive maint.

100%

what mileage are you seeing? under what conditions? you would be surprised how much of a difference things like tire pressure, a/c, and cruse control help out on trips.

I finally got my lisence plates, Alex is registered, and the best deal in my town is BP. Whereas the other fuel pumps like Mobil, Shell, and Citgo(never buy citgo, they're the venezuelans who hate us!) have 91-92 for $3.49-$3.59, BP has 93 for $3.39. No Sunoco close enough and no 94 either, so BP is fine for me. Time will tell if it's good for Alex, I gotta take her out later.

15-16 mpg..like 70% highway...speeds an avergage of 65 i usually go about 70-75...but there are 2 turns where i have to drop speed to around 35-40. no hills. i feel i should be gettin aroun 20 which will make a huge difference in my pocket.

its not my driving habits.....i tried flooring it up and down for about 2 weeks and saw very similar gas mileage. like14 highway instead of 16.
heat is on low the entire time..tires are fine in pressure.

Maybe the MAF or O2 sensors acting up? Or did you recently replace those...

how old are the :
plugs?
fuel filter?
air filter?
original 02 sensor?
last time you sea foamed the vac line?
cleaned the MAF?

plugs..fine
fuel filter--maybe
air filter-new
o2 sensor- original
never sea foamed.

I've heard the O2 sensor can make a huge difference. How many miles are on your car?

I agree, the mpg you're seeing is hideously low, especially for highway mileage. I get 20-22'ish IN TOWN and romping it from time to time.

aside from what has been suggested (02 sensors, clean the maf, change the fuel filter) make sure you don't have any vacuum leaks.

brady..i got 43K on her.....i guess im gonna have the guys look at my car again.........


now...just wondering...would my grill have anything to do with lower gas milage???

If you can, address all the items that Mr.Riviera mentioned before paying someone else to try to diagnose this. Maintenance is a key to getting decent mpg, besides moderate driving habits. And it doesn't take much of an occassional heavy foot to kill the mpg for given tank of gas.

Last couple tanks I've only managed about 16mpg. It's been far far below zero, so my warm up times have been extended, a real mpg killer. And I do not have a light foot around town, but don't drive wildly eitiher.

With the driving habits you mention, I'd expect at least 20mpg. Are you NOT driving around town at all?