What to try next?

[Geodesiq]

I cleaned the EGR plate, got a new cat ($1k OUCH!) and still no mpg change! I barely manage 60mpg highway and under 50 city. I don't see how others can get 85+mpg. Yes I know all about tires. I got the car with the OEMs and then switched to Kumhos. The difference at most is 4mpg. And, if anything, the handling is better with these tires. And it's not me; grannys give me the finger when they pass me doing 62. The air filter looks ok but I'll try replacing that. What's left to try? The car runs fine and I don't hear any unusual noises. Should I replace the EGR valve? Get a valve adjustment? Spark plugs?

[Rainsux]

Originally Posted by Geodesiq

I cleaned the EGR plate, got a new cat ($1k OUCH!) and still no mpg change! I barely manage 60mpg highway and under 50 city. I don't see how others can get 85+mpg. Yes I know all about tires. I got the car with the OEMs and then switched to Kumhos. The difference at most is 4mpg. And, if anything, the handling is better with these tires. And it's not me; grannys give me the finger when they pass me doing 62. The air filter looks ok but I'll try replacing that. What's left to try? The car runs fine and I don't hear any unusual noises. Should I replace the EGR valve? Get a valve adjustment? Spark plugs?

That's about what I get if I drive it like a car. To beat that I have to drive very slowly, use FAS to coast whenever there is a downhill, use MIMA to keep from using the battery so I don't have to charge it later, and keep my tires at 55lbs. With the cold weather and a radiator block I have to really concentrate to get a 60MPG tank. I don't use the heater because I can't get it warm enough to get lean burn. Get some RE92s if you're serious about mileage. Drive for the FCD and nothing else. If you're not over 100MG, slow down until you are. Use a ScanGauge to help keep in in Lean Burn.

These guys who report the very high mileage figures don't usually tell the whole story, and they do a disservice to us newbies. I was very disappointed when I got my car and could only get 50-60 MPG. I was ready to sell it and go back to my fast, fun, turbocharged Miata. But I kept reading here and started to figure it out. You have to do the complete package and never throw part of it away like getting the wrong tires, driving at normal speeds, or using the AC. How fast are YOU going when Granny passes at 62 and flips you off? If it's over 50 you're throwing some of it away.

Sometimes it isn't safe to go as slow as you need to, so just do what's right and take the hit. Otherwise drive for the FCD and you'll see better mileage.

Sam

[Eli]

Sam pretty much covered it. It's really difficult to say what the exact problem is because there are so many differing conditions. The Insight has a steep learning curve. I didn't get my first 70MPG tank until I had owned the car for over a year. This was just through my own experimentation, I wasn't active on the forums then.

Tell us about your driving conditions. You're not going to get 85MPG in stop and go, for example.

Can you cruise along at 100MPG at 40-50MPH on flat ground?

I'm thinking your tires have a bigger impact than stated. 4MPG is only a 6.6% hit at 60MPG. That's what you might expect from a Michelin Energy Saver, but not some crappy Kumho. I'd expect at least a 10% hit from them.

I've averaged over 80MPG while averaging 52MPH over 1200 miles. You definitely have to slow down to get 80+MPG, but usually not to unreasonable levels... just depends on your local conditions and what you consider "unreasonable". A 52MPH average speed sounds slow, but the keyword is average. Most people don't know their average speed, and would be surprised to learn that it's considerably below the speed limit of the fastest roads you travel on.

[Eli]

Some more thoughts..

Your air filter will have little impact.

No need to replace your EGR valve unless you have herky-jerky.

Valve adjustment won't affect MPG, but it would be good to do if the valvetrain is noisy.

Spark plugs would be good to check. Make sure they're the properly indexed plugs for your engine.

[Need4Speed]

I have a cvt and would expect to get about 15 mpg more if it was the manual. I bought the car at the beginning of April with 19k miles on it. The previous owner had a lifetime mpg of 19.0 mpg. I have driven about 5 tanks so far and they are all in the low 60 mpg range. As I have learned how to drive the insight the temps have been dropping so my mpg has remained steady. With warmer weather I was able to drive to work averaging over 70 mpg.

Please detail more about your commute. How many miles? How many stop lights? How many stop signs? At the lights, do you get through on the next green, or does it take more than one cycle? What is your speed?

And from what I know tires can really hurt if they are not the stop ones.

Now what about your driving style? Do you anticipate what is well ahead of you? How far do you coast before having to hit the brakes? The longer you can coast the better. The smoother you can drive the better.

Do you run the climate control in auto, or Econ? If Econ, do you use the ac a lot? If you run the climate in auto the car will never shut off at stops. Do you warm up the car before leaving, or just jump into it and go? Do you park in a garage or outside? What have the average temperatures been?

[gilbertguy]

Maybe there is a fellow Insighter nearby that can drive your car to see if they get the same results.

[retepsnikrep]

Check rear brakes are not binding even slightly. Spin the rear wheels they should do several revolutions after a gentle spin with your hand. The handbrake cables do seize up I've had to replace them on all three of my cars!

[racer26]

I'm gonna echo Eli on the tires issue. The RE92's really are in a class all their own. I put my GoodYear Ultra Grip winters on, and immediately lost about 16%.

Bear in mind also: You have 175's on. You didnt specify the other numbers, which are important to this calculation.

I'm currently running P175/65R14 winters mounted on steel rims on my insight. I run the OE Bridgestone RE92 P165/65R14 on the OE rims in the summer. Steel rims are heavier, and are more rotating mass. Rotating masses have a huge effect on FE because it takes more energy to get a more massive thing up to speed.

P165/65R14:
165mm section width
x 65% aspect ratio = 107.25mm sidewall height
x 2 sidewalls = 214.5mm
/ 25.4 mm/in = 8.44in
+ 14 in = 22.44in diameter
x Pi = 70.49in circumference.

P175/65R14:
175mm section width
x 65% aspect ratio = 113.75mm sidewall height
x 2 sidewalls = 227.5mm
/ 25.4 mm/in = 8.95n
+ 14 in = 22.95in diameter
x Pi = 72.09in circumference.

72.09/70.49 = 1.022, or a +2.2% distance travelled.
This means, for every 100mi the odometer shows (and therefore, the FCD is calculating based on) the car has actually travelled 102.2mi.

P175/70R13:
175mm section width
x 70% aspect ratio = 122.5mm sidewall height
x 2 sidewalls = 245mm
/ 25.4 mm/in = 9.65in
+ 13 in = 22.65in diameter
x Pi = 71.16in circumference.

71.16/70.49 = 1.0096 or +0.96%.

This will affect your MPG as well. If you're using 1 gallon of gas to travel 60miles on P175/65R14, then the car thinks you've only travelled 58.7mi, and will read 58.7mpg.

[ghammerly]

Other than driving stile and conditions you have 60psi RE-92's and maybe sending your fuel injectors for a clean-up. Also check your toe (0 toe) and make sure your brakes and wheel bearings are not dragging.

[kennysmith]

I live in a hilly area, drive 65mph and during the cold and rain have trouble getting more than 55mpg. I drove 700 miles at 50mph during nice weather and averaged 80mpg so I know it is possible.

No one has yet mentioned rain and hills, but they are huge factors.