regular unleaded vs. premium gas
 

I read an a few articles in the NY Times that spending the extra $ for premium gas is a waste. See article link below. What do people use in their GLS 450?

http://www.nytimes.com/2016/09/23/au...ular.html?_r=0

I've been on the planet a long time, and have used a lot of gas. I have a '67 GTO (Pontiac not Ferrari). The GLS 450 engine shows a 10.5:1 compression ratio. The GTO is 10.75:1. MY '14 ML350 is 12:1 !!! I disagree with the author and he contradicts himself. Unable to cut and paste, but early in the article he says your engine will let you know it doesn't like the gas because you can hear it knock. Later on he says you won't hear it knock because engine mgmt will change the timing when it senses knock. Can't have it both ways.
I don't have experience with turbos, but you can see that MB was able to lower the comp ratio and gain power by turbocharging. My ML gets part of it's power from the 12:1 comp ratio. I will lose some power if I drop the octane. The GLS will like lose less power at lower octane because the turbos don't care. If you drive on the flat, my personal opinion is you can use 89 with no noticeable diff. If you need acceleration going up hills a lot, stick with 91 or 93. The GTO only knocks when the timing slips, which happens due to the mechanical nature of the system.

Wow - you spend 70 grand on a vehicle and you are worried about spending an extra $1-2 per week on gas? Maybe you should consider a Korean vehicle.

I have never put anything <91 octane in any of my vehicles that recommend it. Would never occur to me. Like not changing the oil when required. Penny wise, pound foolish.

The general guideline I offer to my customers - 1/2 the savings between "mid-grade" and "premium" will be lost to lower-efficiency/lower-MPG - less "boom" in the fuel frankly.

In our state at the moment the difference is $.20 per gallon - on a 20 gal fill - the full price differential is $4.00 - after efficiency loss - net "savings" about $2.00 that fill.

Depending on your drive-miles-yr OR increased fuel-prices/increased differential - let's say mid-grade and premium are $1.00 per gal differential - or you're driving 30K miles a yr - then the savings paradigm changes.

To maintain efficiency during ownership - annual/10K-mile fresh airfilter - and I personally recommend 1/2 bottle Stabil Marine Fuel Additive no more than 1/2 bottle every 5K/6K miles - again my personal recommendation.

People should just follow the manual since the car is engineered to run at that fuel. Higher end benz owner should not worry about gas prices. If they do they should not be buying a benz or they had bought the wrong car.

penny wise pound foolish

Not direct "apples to apples" but for many years I drove a Lexus LS430. We constantly got into the debate about regular vs. premium until one of the members actually did his own survey (yeah - only a sample of 1, but pretty convincing nonetheless). He found that if he calculated the cost per mile for fuel, his car cost the exact same amount per mile on regular and premium. He just got fewer miles per gallon on the regular. The engine management system protected the engine by retarding the spark, but performance and fuel economy suffered.


I'll agree with the poster who said "If you bought a MB and then want to save $X/week on fuel, you've bought the wrong car."

Note the wording Recommended vs. Required. MB uses the word Required. That's good enough for me to know what MB wants to do so I get the most enjoyment out of the car. Use Premium as it is Required not Recommended.

Have a mate here in OZ who used to work in the petrol business told me they called standard "slops", it was all of the old crap in the lines, whatever they could use to make petrol. . Premium was distilled from quality oil, then each brand adds its specific additives
Nigel

It is recommended because the car will run on crap gas but it is not good for it. Look up predetermination and octane. Yes the car will protect itself but it will have to knock first and that causes damage.

In the US this is not true. All the fuel starts the same then the premium gets additives. Medium (complete waist of time/money) is mixed onsite between the two.

Nice Info...

Err, no::

Regular gasoline has more energy content per unit weight or volume than premium. So, there is less boom with premium than with regular.

As to turbocharged engines, there is a lot of ECU control over these engines that was not around in the muscle car era, so comparing a 67 GTO engine with a modern auto/motorcycle engine is fraught with peril, and most assumptions on the older technology being the ame on the newer stuff will be flat out wrong.

Back to gasoline: If you are not flooring the throttle, you don't need premium gasoline in any Merc product. I use mid-grade gasoline in my 450 GLS and in my S600. They run just fine. I tried some regular gasoline in my 450 and the engine would occasionally sniggle (a precursor to ping).