Gettin' 21-22mpg you should get 28-30mpg

[KdCass]

When I first got the car I was getting 21mpg, and the car felt fine.

I changed the plugs (denso irridium), air filter (K&N drop in), fogged the airbox (3in tube), and changed the precat o2 sensor.

I did them one at a time each one bumped the gas mileage up.

Now if I reset the mileage comp. at 60-70mph cruise it will get 37 maybe a little more. Compared to before it would get 27.

Im really impressed at what a little maitenace and slight modification can do.

Driving 'normal' I get 28-29, driveing fast I get 26-28. Before I got 19-21 and 20-22.

-Dave

[robcarync]

i was getting 18 MPG...but i changed the thermostat...and that did the magic trick...now getting 30ish MPG...

there is nothing better then jumping from 18 to 30 MPG...makes me happy!

[losichu]

I wish I were so lucky. I get 20 - 25 mpg and I've changed the spark plugs, air filter, fuel filter, and just today the 02 sensor. Why did you change the thermostat? That seems kind of odd to shoot up your gas mileage, but I'm interested.

[KdCass]

Losichu, give that 02 sensor a little time. I saw the biggest improvements from it.My check engine light was only intermittant (sp) and it helped alot.

-Dave

[mplatt911]

I was getting like 25mpg and now hit 29mpg this week. This is in a 95 ti with auto. Replaced the thermostat so it was always running right in the middle vs. cold to mid range. I was also trying out 87 octane and went to 89.

[KdCass]

The manual to our cars says that the minimum octane is 91, its a high compression engine 10:1.

Sounds risky putting anything less, I use 93 always.

-Dave

[97Hellrot318ti]

Originally Posted by KdCass

The manual to our cars says that the minimum octane is 91, its a high compression engine 10:1.

Sounds risky putting anything less, I use 93 always.

-Dave

I wouldn't call it risky putting in anything less than 93... I think the manual actually says 90, but I've yet to see 90 or 91. I use 89 (Mid-grade)... I think I may switch to 93 once I put some more performance oriented upgrades in place.

[cali-ti]

if the thermostat fails open, your engine never gets up to proper operating temperature and it continues to run rich (startup mode) ... at least this is my understanding. you're basically using more fuel than needed and get worse gas mileage. i would also think it would be bad for your cat. someone with more knowledge please confirm/deny/provide more info.

[robcarync]

a while ago my o2 sensor was out with the CEL coming on intermittently, but i never saw any mpg increasage.

my pops noticed that the car was taking a while to heat up, but i never noticed it because it took a while as long as i could remember to heat up...i didnt know what was normal for the length of time to heat up...

and he suspected a thermostat and all of a sudden, the car heats up fine, and im getting 27 mpg right now!

it probably wouldnt be benefitial unless for instance you think your thermostat is bad and it takes a while to heat up, but basically your engine runs more efficient when its at the optimal temperature (in the middle), so if it takes a long time you get your car heated up and the engine is cold longer, more gas gets pumped in trying to heat it up.

[LeslieRL]

We've just made a trip of exactly 400 kilometres using three quarters of a tank. Assuming the tank holds 40 litres, that's 7.5 litres per 100 kilometres (as we measure it in New Zealand) or about 37 mpg. But that's imperial gallons, which are different from US gallons. 1 US gallon equals 3.79 litres. 1 imperial gallon equals about 4.55 litres, so in US terms we used about 31 mpg.
But I'm not sure how much the tank does actually hold.

[mplatt911]

The thermostat being stuck wide open will definitely cause issues with mileage and cats. I had an a set of cats go on my Audi because car ran too rich for too long. I also had little heat on the cold winter days in northern NH.

On my 318....My fuel mileage went up 3mpg , to 29-30, with the thermostat change. Worth the 30 minutes of work, IMO.

I am sticking with 89 octane. The engine has a knock sensor and adjusts accordingly. Unless I'd see 35 mpg with it. I did notice some intermitent knocking with 87

[pdxmotorhead]

I get 28 to 30 on my 95ti. My manual says 89 octane, I find it makes
power fine on 87, and I get the 30 on 87, 28 on 89, 25 on premium.
Which kind of makes sense in our oregon climate, Lots of humidity,
Higher percent ethanol than average for most areas.
(We get a full 10% ethanol here for emission control )

Dave

[losichu]

Well, my car warms up fine so I don't think that changing the thermostat is going to help anything. I do have a constan CEL now and it says lambda control #1 is causing the problem. I was told to check the vacuum hoses. I feel dumb for asking this, but where exactly are they talking about? Ive been looking but have had no success whatsoever finding any vacuum hoses. Please help as I feel this is what is causing my miserable 21 - 23 mpg

[cali-ti]

lambda #1 would be the oxy sensor. what told you "lambda control"? never heard it that way (other than in the ETK, they list the oxy sensors as lamba probes)

[losichu]

The DIY in the links forum said that code 1222 is the lambda control #1. I have changed the 02 sensor and its still not working. I'm checking vacuum hoses but I don't know where to start looking.