cant afford it?? its only about a $3 difference

 

Not mention that lower octane gas increases fuel consumption in these cars, so at the end of the day, he's not saving anything.

 

Really? Never heard that before. Don't doubt it though, I guess 93 is more considerable now.

 

You mean turn around and go the opposite direction on the same road? I never thought about that, the road is fairly flat, but perhaps wind could have helped?

As far as the 87 vs 93 debate goes. I use 93 for many reasons, one, you ususally don't get the additives in the 87 (which help clean engines, and provide a secret blend that help achieve more fuel economy, etc). Not only that, but the higher octane means that the combustion temperature is tighter, allowing the engine to adjust better for timing and to get optimal power. While 87 octane won't "harm" the engine, the engine has to compensate for the additional knocking (haven't really heard of ping) which will retard timing, resulting in less fuel economy and power. But, running 87 will lead to a dirtier engine, and as much as retarding the timing will do, you will still have some accidental detonation in engines designed for 93, will can cause some harm, but more importantly, can cause undesired movement, especially when coming to a stop, the car can lurch forward, which is extremely dangerous in stop and go traffic and parking lots. And at times can be a bit concerning.

While I haven't noticed this much in the smaller engines (such as the c300), my G37 used to have a much worse response to regular 87 gas. Regardless, running 87 doesn't really "save" much, if anything at all. Between the worse fuel economy, and the fact that it usually only runs 20 cents more expensive than 87 octane for 93, (I actually get it on weekends at mid-grade pricing for only 10 cents more), the difference in price is MAYBE $100 a year in savings IF you get the same fuel economy. (Assuming price is 20 cents different, you average 24mpg, and drive 12,000 miles a year).

But the fact is, running 87 will get poorer mpg's (about 1-2mpg in my experience) the cost actually equals out for 1mpg less and ends up costing MORE if you get 2mpg less. Combine that with the fact that you don't get the same performance, and makes your engine dirtier, it almost seems like a no-brainer if you ask me!

As far as how good fuel cleaners are, and which are better than others. I use Techron for two reasons, one, it is the only other fuel injector cleaner recommended by Mercedes-Benz as a substitute for the official MB cleaner. And 2, I can pick up a bulk case at Costco for about $6 a bottle (average out).

I have heard that some other cleaners have additives that can dry out or crack fuel lines. Also, you should not run below 1/8 of a tank because over time, dirt, particles and other contaminants will settle at the bottom of your fuel tank, you increase the chance of picking these up and having the engine ingest these particles/contaminants when the fuel level gets lower.

 

That's not quite what I've read. Supposedly fuel is picked up from the bottom of the tank, so if there is crud settled at the bottom of the tank, it'll get sucked in regardless if your thank is full or nearly empty. But the job of your fuel filter is to stop all such contaminants from entering the engine. Running an occasional bottle of fuel system cleaner should help, too.

As for the reason not to drive on a nearly empty tank - the fuel pump on most cars is at the bottom of the tank and is submerged in gasoline, ie. it is cooled by gasoline. If gasoline level is too low, there may not be enough cooling effect and it may decrease the useful life of the fuel pump. At least that's the theory. None of my cars ever suffered a failed fuel pump, despite me running them on fumes on numerous occasions.

 

Makes much more sense to me. That is perhaps the only thing I haven't researched and rather just took the "rumored" word for it.

 

Part Two of my car's engine being awesome:
Insane Fuel Economy:
Here is my mixed city/highway driving at 28.4mpg


And now here is my latest trip from work to home (about 90% highway):


Yes, you read that right, 34.6 MPG... Lol. I set the cruise control to 62mph (I guess the average speed is only 59 because of the short distance from office to highway and highway to house is slower than 62mph).

Boy I love my car!

 

So do I . Below are a couple of my fuel figures.

 

What's your all-time average? Ours is about 20.8 MPG. Terrible, really. My 530i gets better mileage than this, but then again, it is not AWD and is manual.

 

Lifetime mpg based on gas receipts is at 23.4 mpg, having now 38,000 miles on the clock.

 

I thought I would give this a shot today coming to work - I averaged 67 mph on a mostly highway commute doing 70-75 (just a couple miles of city driving on each end)...29.9MPG, could easily get this in the 30's by slowing down and using cruise control around 65 or so...not too shabby.

(btw - I run 93 octane in this car from the same Sunoco station every time)

 

I don't know how you guys do it. I can't get more than about 25 MPG out of ours, even if I baby it.