Lower Octane...Less $$ more MPG!

[rvanengen]

Well...decided to ignore the octane warnings by MB (they only want "Premium") and put some 89 octane in the car on the last tank...and guess what? :-)

• It seems to run better
• High temp miss is less noticeable
• I got almost 2 mpg better! (well 1.6)
• It cost less! (I am not a rocket scientist)

So...I topped it off with 87 octane, and we will see if that introduces any pinging or knocking. (fingers crossed) If I get some pinging I will go back to 89 and let it run a bit longer to get some more definite numbers.

For now, it looks better, and I was driving harder, faster and with more A/C on and still got better MPG! http://www.gassavers.org/garage/viewgaslog/408

[SVOboy]

Sweet deal! Perhaps the car has gotten too tired for high octane,

[rvanengen]

Never thought about it that way...but it might be! I am sure that I am tired of premium gas and premium prices!

This is certainly a reverse of my last few cars... a 97 Crown Vic Police car...and a 96 Bronco that both had a strong taste for 93 Octane...or they would ping like crazy!

[SVOboy]

Have you thought about selling the MB anytime soon?

[rvanengen]

Not really...it runs well, gets at least acceptable MPG so far, and I am really wanting to use this car for an EV conversion in the near future since it is RWD and has a 5-speed. Not to mention, compared to other smaller cars, it is built like a tank and was actually cheaper than a Honda of similar mileage and condition ($3k) and had 95k miles on the clock when I got it.

As a plus, my 2 year old LOVES to ride in papa's car... Annoys my wife...he doesn't like the wagon as much.

[SVOboy]

Gotcha...I knew you had EV plans but didn't know if you were going to attempt it on such a heavy car. I want to go EV on my car, it's light and aerodynamic, but without much room! The tradeoffs we make I guess.

[rvanengen]

Yeah...that had me worried at first, but the car is just at 2900 lbs and has about a 900lb cargo capacity stock...so I figure it should be good especially since I can beef up the rear suspension and get larger brakes (400E brakes are a popular upgrade) if needed. Should be fun.

There is another list that I am on that has several people doing BMW 318/325's pretty often, and they are about the same size/weight as the 190.

[yo vanilla]

in the past i have recorded losses by using lower octane gas, which makes perfect sense since the engine retards timing and therefore runs like it needs a tuneup.

i would guess that your old 190e might need some work, with everything listed. for instance, if it is running better now, with timing pulled due to the lower octane gas, well was the timing set right in the first place?

[GasSavers_Ryland]

I've noticed some 91 octane around here has 10% ethonal, and when i use that my mileage drops by a few mpg, where the 87 is pure gasoline at most of the gas stations around here, but it does varry.
if it's a new enough car with a knock sensor they it should self adjust to meet the fuel, at least to a point, so you might never have it knock, or not very badly.

[rvanengen]

Originally Posted by yo vanilla

in the past i have recorded losses by using lower octane gas, which makes perfect sense since the engine retards timing and therefore runs like it needs a tuneup.

i would guess that your old 190e might need some work, with everything listed. for instance, if it is running better now, with timing pulled due to the lower octane gas, well was the timing set right in the first place?

Who knows? I am not sure the timing is correct now, I guess I will have to see if I can find a timing light and check it one of these years.

I might try another set of plug wires and actually check the cap/rotor and even the coil.