I did a search and found nobody was talking about this, so check this out: My 02' CLS has always performed well since I first baught it but I was always shocked at the shitty gas mileage. When I joined this site everyone pretty much had the same thing to say - up to now I only have 73,000 miles, so I didn't think about it.

A few days ago I'm driving back from Miami to Birmingham (12 hour drive), so I use this as an opportunity to try some fuel injector cleaner. Now, mind you, about 15 years ago I tried STP fuel injector cleaner on my other car and saw NO improvement, so I said fuck it and never looked back again.

This time I stop at AutoZone to try this again. This time they have 20 different brands of fuel injector cleaner (there was only 2 brands back then). I must have stood there for nearly an hour trying to make a choice. They all had the same instructions with no one having any kind of "guarantee" that theirs is the best on the market. THIS time I ignored STP and went with concentrated Gumout.

I burned the rest of the gas out of my tank, then filled up and put the bottle in my tank. I drive and burn that whole tank and fill up again. This time I take it through the test. I'm doing 90mph for about 100 miles and the fuel tank needle didn't move!!!!

Okay, so I average about 110mph for another 120 miles and I barely burned 1/4th of a tank!!!!

For about the last about 200 miles of the trip I burned only 3/4ths of a tank. I'm still shocked. I baught the concentrated Gumout fuel injector cleaner. This stuff really works !

 

I'd bet there were other factors involved. Also the gas gauge is not liner. Only way to calculate gas millage is by MPG.

The mileage you get in a 1/2 tank varies by driving, weather, tires, wind, etc.

I've used the same stuff from time to time in various cars & never saw much of a difference.

You want a REAL difference? Run a can of Sea Foam through your engine. That cleans out the internals.

 

Yeah, I'm more than aware of driving factors. I didn't start driving yesterday and this isn't my first car. I've clocked thousands of miles in several different cars - driving through several states - and as I said previously I have 73,000 on my current car. Having done the SAME trip before in the SAME car and having had shitty gas mileage, and all of a sudden a change like this - getting significantly more gas mileage - warrants letting people know what's up.

 

Wasnt too clear on the Sea Foam Directions just looked at there web site. Can you give me directions on use?

 

So tell me this: How is it that my gas mileage improves even though I'm driving faster than I normally did the previous trip? Secondly, why would I be so impressed if I had already said my previous experience with fuel injector cleaner had made me skeptical? It's just a question. You don't have to believe me - you don't even have to answer the question. The concentrated Gumout worked for me. As for the sea foam I'll check it at some later time. But my engine is not that gunked up to begin with.

 

Florida is flat. If you have a strong tail wind it will push your car & you will get better mileage.

Did you take the turnpike & 75? They have paved those roads the last year & smooth roads help with gas mileage.

Did you get new tires? Or wear your tires down? What was your tire pressure? Those contribute to gas mileage.

Was is very hot?(it's FL in summer of course it is) Warm air is less dense, hence effecting gas mileage.

I could go on.

I never said it didn't help, I said there are other factors involved.