S70 fuel economy or lack of it...

elchopperfreak · Post by **elchopperfreak** » 09 Apr 2011, 18:16

Our 1999 S70 T5 car, with less than 50k miles, shows on the computer that avg miles per galon is a mere 14.8
This is an average of mostly city driving since the car has not been on the highway lately.
I have read it should be at least 18 normal 20 mpg avg.

What would be the steps or items I need to check in order to achieve the mpg that seems to be normal for that car.
It has not been mistreated nor hot rodded, just normal use.

Thanks for the help

Post by **Glencoeteen** » 09 Apr 2011, 18:21

ehhh thats about right, my T5 does about that with pure city driving,

sliptones629 · Post by **sliptones629** » 09 Apr 2011, 18:32

Less racing stoplight to stoplight....

elchopperfreak · Post by **elchopperfreak** » 09 Apr 2011, 18:41

Theres no racing unless my wife is hotrodding and I dont know it..

What would normal things be?
Change air filter ( who has best prices for K&N ?)
Plugs
Is it time to change Oxygen Sensor?
What else?
Thanks

Post by **kcodyjr** » 09 Apr 2011, 18:59

Take it out on the highway and give it a good kick in the rear end. Stick your toe right out through the grille.

Then, come let us know how it feels. If it's in need of a tune-up, then throwing parts at it may well improve mileage.

If nothing's wrong with the engine, then swapping out parts won't help. If you must do something now, pour a bottle of Techron into a half tank of premium fuel, and take it for that heavy-footed Sunday drive I mentioned.

You are running 91+ octane, right? Good tires and alignment? Have you changed the transmission fluid since it was new?

elchopperfreak · Post by **elchopperfreak** » 09 Apr 2011, 19:17

Cool,
Mostly premium gas, try to be 89 oct and up
Tires are 6 months old
Alignment is so, so, ( roads here are going to hell quickly, bad repairs, caribbean weather..)
Trans, i dont know, when or if it was changed, got to ask.

Thanks

Post by **kcodyjr** » 09 Apr 2011, 19:39

A bad alignment will kill your mileage, in any car. The tires have to fight each other and the pavement.

Mostly 89+? You can get away with 89 in the NA, but the Turbos really go to hell in a handbasket with anything less than 91.

Run it down, dump a whole big bottle of Techron in it, and fill 2/3 to 3/4 with the highest octane you can find. Do not refuel again until you're below a quarter of a tank. Get a good mix of highway and city driving done. Thereafter, stick with Super.

You should also drain and refill your transmission fluid. If it gets worn enough to turn brown or smell burnt, power isn't reaching the wheels like it should, and you'll have to step on it harder for the same result. I've heard it should be done every other oil change; don't flush, just drain and replace what's in the pan. Search around the forum for guidance on which transmission fluid to use depending what transmission you have.

What follows, I was hoping to test by having you drive it hard. If any ignition components are worn, performance will suck, and mileage with it. By contrast, clogged air and fuel filters will have a minimal effect on mileage, since the ECU will still be able to keep the two in balance, and only ultimate power is compromised.

Have you inspected the spark plugs lately? Distributor cap and rotor? Also, can you find a really dark place at night? Remove your spark plug cover ahead of time, disable your daytime running lamps, then go to that dark place. Turn out all the lights, lift the hood, and watch the engine idle. Give it several minutes so you know your eyes are fully adjusted. If you smoke, don't, the glow will be enough to mess up your night vision. If your spark plug wires are worn, you'll see blue arcing.

The other wear item that can really affect mileage is your O2 sensors, but they should turn on the CEL if they've failed.

elchopperfreak · Post by **elchopperfreak** » 09 Apr 2011, 20:04

Thanks.
Problem with fuel is , we have been getting lower and lower octane at the pump, for a higher price. Some pumps dont even carry premium anymore,people are not buying it, but anyway, will do so.
Changed plugs, checked everything not even 6 mos ago, but will do so again.
Have no seen any arcing on the wires ( although that would make it to misfire and if grounded quit??, at least in bikes it does)

Thanks for your help.
Interesting that other t5 owners are getting similar milage, feels like its sucking heavy on the gas.. Or could be the prices??

Post by **kcodyjr** » 09 Apr 2011, 20:26

It could be the prices, and I understand your pain - but, in the final analysis, you're going to get better miles per dollar(?) with the high octane than with the low. If your availability issues get worse, you should start looking for an anti-knock or octane boost product.

You sounded like the kind of guy to keep an eye on his vehicle, but I had to ask. That's why I suggested the hard drive, if there's any lingering issues with ignition, a good stomp on the pedal will show you.

Post by **jblackburn** » 09 Apr 2011, 21:08

Since gas went above $3 again I haven't run anything but 89. It runs fine in a turbo.

If you've got no check engine light or anything, just poor gas mileage with no other symptoms, I'd consider changing the front O2 sensor. My T5 did the same thing about a year ago and I wasn't getting over 20 mpg at best on the highway. A new O2 sensor put in, and it went back up significantly.