My 1998 S70 T5 is at 135k miles. It gave me some troubles in the past year, but now it's running well again, so I guess I'll keep it a bit longer. In its better days, I saw 32mpg highway and 24mpg combined. Now, I get 25mpg highway and low 20s combined.

Here are a list of things that have been replaced in the past year:
fuel filter
spark plugs, wires, distributor cap, rotor
ABS module
thermostat, ECT
front driver side axle
front brake pads
rear brake pads and rotors
heater core
evaporator, drier
tires aligned in Nov 09

Will I ever see the same mpg as before? What can I do to help prolong the life of the car and maybe gain back some mpg?

 

We got the same low mpg. Any suggestions to improve gas mileage? can we use 87 octane? Just bought last month 98 s70 .

 

You can run 87, but obviously its better to use the higher rated gas and recommended.

 

Tire and tire pressure are a good place to check. Also, I run 93 octane. I have run 87 and 89 and get less mpg. The better gas milage off sets the price/cost. Also, running lower octane can cause you to burn your valves (so I've been told).

OEM plugs help. Make sure they are gapped properly and change your air filter. I use a drop in K & N filter.

You may want to get a Scan Gauge II. It has saved me a lot of money in tweeking my driving techniques. I get 25 mpg in my T-5R and 25 mpg in my 960. I was getting 21 in both cars before I got the gauge. I usually drive my cars in the S transmission mode. I like the power & kick to be there when I need/want it.

 

I am running 87 octane, but that's what I've always run, I think ... I assume 87 is the lowest they had in Texas too. So, that hasn't changed.

All my tires are at 37psi right now.

I think I gapped my plugs properly. Is there anyway to tell if I didn't? There aren't any misfire codes.

I think my air filter is fairly new, but that's easy enough to change.

Thanks for the help.

 

Did you use oem plugs? Mine are gapped at .028. As for the octane, it is suggested that you use 91. Do you have the trip computer? As explained in another post, milage goes down a little in the winter. Something like 2 to 3 mpg. Also, don't let the car sit and idle to warm it up, that is not recommended nor is it good for the motor. I'm still getting 25 mpg, even with it being cold but I almost NEVER drive over 63 mph. That seems to be the breaking point with my milage.

 

I used Bosch platinum from FCP Groton. I do have the trip computer, which is how I watch my mpg.

My daily driving is much different now than before. Although my main driving is local, the daily commute to work is only 5 miles, so the car doesn't spend as much time as before at the optimal temperature. I've never started the car and let it idle; I'm in SoCal now where it's seldom that cold.

I'll add that I've had oil leak problems before. My valves leaked, and I was losing oil for a while pretty fast. I know that I drove with less than optimum on many occasions. What kind of damage would running with low oil cause, and can this be a cause?

 

What is a Scan Gauge II? What does it do?

 

Running with low oil can cause strain on your engine, and the parts that need consistent lubrication while driving won't be getting enough to let the car run normally, and eventually and quite quickly bust your engine. It's wise always to keep it topped up, especially if you have an oil leak.

 

Running anything other than premium on a car with a turbo, especially a HPT, is a recipe for failure.