Does Shell Optimax Unleaded work for MB?

[desrobinson]

I've always wondered if the special fuels that Shell produce work in MB cars or do they screw up the engine.

Has anyone any experience with these?

 

[jberks]

There have been a number of discussions on this and I have done some tests myself. The general view seems to be that older cars - say pre 92 roughly get a real benefit in improved MPG and performance. On newer stuff, with later management systems, it made no difference whatsoever. Personally I'm back to running on the plain old 95 octane normal stuff.

 

[desrobinson]

Interesting. So the claims that Shell make could, generally, be false.

Anyone tried these fuels out on a Kompressor system?

 

[3146bj]

I've used Optimax in a 1993 E280 W124 with an improvement from 10l/100km to just under 8 on long runs and from 13 to about 11 in the city. In general, Optimax offers gains where the engine management system includes a knock sensor to take advantage of the higher octane rating (98RON vs 95 or 91 here in Australia) and/or a feedback loop which corrects the mixture to run at optimum mixture or can meter the fuel injected by mass. The latter requirement is needed to take advantage of the higher specific gravity (0.78 vs 0.72 for ordinary unleaded) by reducing the volume of fuel injected to get the same energy input.
And we measure our fuel economy by volume not mass, so we get better mpg or l/100km for the same volume of denser fuel.

Cars without the above features rarely gain from using Optimax or similar higher octane and density fuels, eg absolutely no difference in economy with an early Land Rover Discovery. Be interesting to see how an old high performance carby engined car (Cooper S or Lotus Cortina) would go.

Contrary to popular belief high octane fuels (not high density) do not offer any improvement unless the ignition timing is changed by a knock sensor system or by manually resetting to take full advantage of the engine compression ratio. Any performance change noticed is what our medical brothers call the "placebo effect".

 

[SLinKyjoe]

the claims Shell used to make were stopped by the advertsing authority. their web site gives details.
BP have ultimate which has been independantly tested and seems to offer the benefits.

 

[clive williams]

I always use Shell Optimax in my 500E where and when available - there aren't too many convenient outlets around here (Leics-Hinckley). I have consistantly noted up to 10% improvement in mileage for a 5-7% extra cost plus there is an obvious improvement in power and response. The same improvement also comes with high octane petrol (super unleaded) but the cost is usually too great.
My other rule is stay away from supermarket petrols as they don't contain the same detergent additives. I've had previous cars gum up as a result, cured only by expensive injector cleans.

 

[philharve]

Optimax in MB engines

A work colleague who drives a late nineties Land Rover Discovery mentioned to me that he nevers uses 'unbranded' supermarket fuel because it lacks the detergent properties of better quality 'branded' fuels. His main vehicle is the Discovery, a 2.5L diesel, but he owns a much older 'second' petrol car, a Vauxhall, I think. He switched to using branded fuels on both cars some years ago when he noticed a significant improvement in performance in the older vehicle. He claims there was also a worthwhile improvement in efficiency in the Discovery.

My MB runs, apparently, quite happily on supermarket fuel but my colleague's comments got me thinking about the possible long term consequences of cheap fuels on modern engines. Is there anything to be gained to switching to quality fuels and to a higher octane fuel such as Optimax?

Yesterday I filled up with Shell petrol (95 octane) and noticed the pump immediately to the left dispensed Optimax (98 octane). I was tempted but resisted the opportunity.

I will stick with Shell for the next few weeks to see if there is any difference in either performance or efficiency. Shell filling stations are not that common where I live and future refills will mean a 16 miles detour. Supermarket fuel is by far the most common - I use ASDA - followed by Jet, Gulf and Texago.

Optimax is 99p/litre. Unleaded (95) is typically 92p/litre but 88p at my local ASDA. Shell unleaded is 91p/litre.

My 'experiment' will therefore cost me about 3p more per litre but it might return better fuel economy and keep the engine and fuel injectors cleaner. This could translate to better running and lower running/maintenance costs. I am willing to pay an additional 3p/litre for these benefits. However, switching to Optimax is much more difficult to justify being 10 -12p dearer. On average, switching to Optimax would mean an additional GBP6 - 7 per tank. Would I ever see a return upon my investment?

My MB handbook states I should use 95 octane. What would happen if I went up to a 98 octane fuel bearing in mind that I drive a car supercharged engine?

I have driven about 6 miles on Shell petrol since the refill and it's difficult to say whether there has been any immediate improvement. It runs well, possibly smoother. I suspect if there any gains to be made I will probably notice them later as the detergents start to remove any gummy deposits that may have built up in 95,000 miles.

What do other MB owners think? Is it worth paying the extra?

REGARDS Phil

 

[SLinKyjoe]

My MB runs, apparently, quite happily on supermarket fuel but my colleague's comments got me thinking about the possible long term consequences of cheap fuels on modern engines. Is there anything to be gained to switching to quality fuels and to a higher octane fuel such as Optimax?

My MB handbook states I should use 95 octane. What would happen if I went up to a 98 octane fuel bearing in mind that I drive a car supercharged engine?

What do other MB owners think? Is it worth paying the extra?

REGARDS Phil

you wont see any benefit by using 98ron. not if your car is set up to run on 95ron. Using supermarket fuels shouldn't cause any problems but as they dont have detergents in they wont clean your engine.

I ran my previous SLK on sainsburys 95 stuff and had no problems. the new slinkymobile is meant to have 98ron which means Optimax of that new Tesco 99ROn stuff. Mercedes recommend that you dont use a 98 set up engine at fulkl throttle with 95ron in it. they also suggets you will see less performance and fuel economy. however, a 95ron set up wotn go better with 98ron in it.

 

[turnipsock]

I think I have made these comments before...

When petrol comes out of the refinery, each company has it's own gantry and the additives are put into the tankers. That is; BP tankers get one additive, Shell get another, etc.

The supermarkets don't get any additives, hence the cheaper prices.

The guy that is in charge of the tanker terminal at Grangemouth wouldn't go anywhere near a supermarket petrol station.

I have been using BP Ultimate for the last few months. I noticed a difference in the feel of the 230TE as soon as I put it in. The engine seemed slighty more responsive.

I have never tried checking the MPG as it's not very easy to test fairly. You can easily drive with a light foot if you are trying to improve your MPG.

 

[philharve]

Branded fuels

I'm almost through my first tank of branded fuel (Shell) of 98RON unleaded after almost 9 months of using ASDAs non-detergent 95RON. Any difference? Well, I think the running is a little smoother, the pickup a little sharper but I'm not expecting any real advantage in terms of mileage. Is using a branded fuel being kinder to the engine? Dunno! Probably! Maybe I should refer the matter to Mercedes?

I will fill up with Shell Optimax next time but it will cost me around £6 extra for the privilege. I can't imagine i'm going to notice that much difference. I think it would take a considerable improvement in mileage to make the swap worthwhile.

I will probably revert to ordinary branded unleaded fuel if it means smoother, quieter running. You can 'feel' the difference over supermarket fuel but I need convincing that it will make that much deifference in the longer term.

REGARDS Phil

 

[Bluegrass]

I used BP Ultimate (103.9p) in my 2000 320CDI for the first time in this car today and noticed a smoother engine with slightly improved acceleration. Previously in an old Volvo 740 Turbo at 190000 there was a significant improvement.

On another point where is the engine number located on the block. The log book says unknown and i want to update it.

Thanks.

 

[tom7035]

On another point where is the engine number located on the block. The log book says unknown and i want to update it.

Thanks.[/QUOTE)

Usually on the block just above the transmission mounting face.

 

[davidsl500]

The SL runs fine on asda fuel - and its a good 4p a litre cheaper than anywhere else. I do use Redex with it as well - a 500ml bottle from Wilkinsons would you believe is £3.19 and good for 200 litres of fuel - thats 1.6p per litre and cheaper than branded petrol.

I do shove the occasional tankful of the good stuff in as well though....

 

[philharve]

I'm now on my second tank of Shell unleaded and the engine does seem to run smoother. The pickup seems to have improved too. However, it is difficult to resist these new found benefits and the extra few horsepower. The almost enitable result has been that I've been a little more lead-footed than usual. If there were any more miles-per-gallon to be had by using a branded fuel, this has largely been negated by a more enthusiastic driving style.

So ... it would seem that the switch to a branded fuel may well result in a higher-performing and cleaner engine but whether or not there is also a worthwhile impovement in fuel consumption, that is still in the hands of the driver.

I will try a couple of tanks of Shell Optimax next and then switch back to ASDA supermarket fuel and compare results.

I thought I read somewhere, probably in the MB Owners manual, that additives, e.g. Redex, was not recommended. MB don't say why. I have used Redex and other additives with previous cars and overall I believe they were beneficial and contributed to the longevity of the engines. When I stripped them down after mega-miles they were remarkably clean.

Perhaps Redex+supermarket fuel is a cheaper alternative to using branded fuels with detergent additives. I wonder if there has been any research in this area? Is Optimax and similar high grade fuels merely a gimmick?

REGARDS Phil

 

[Big Jim]

What do the Touring Car racing boys use? :Oops:

 

[philharve]

I'm now on a tank of Optimax and my kompressor engine runs just fine. Whether it's smoother and more accelerative compared with Shell unleaded I cannot really say. It's certainly more expensive, that's a fact, because it cost me an extra GBP6.00 to fill up. Unless I see a proportionally improved MPG I don't think I will stay with Optimax. Switching to branded unleaded (with additives) from non-detergent supermarket fuel is probably worth it in the long term; it's kinder to the engine and will keep it clean.

High performance fuels such as Optimax probably have a greater impact on older engines by removing gummy deposits but I've still to be convinced that they have much to offer modern engines.

REGARDS Phil

 

[SLinKyjoe]

BTCC boys use performance unleaded. it is a race petrol normally about 102RON. can be up to 104RON. however it doesnt have any aditives that are for use in road cars, so if you were to use this fuel, your car could do with an engine strip down and bits replacing every 1000miles or so. Its for sale at most race circuits. normaly only to race cars teams.

My WRX needed its ECU resetting after one tank of 95RON. not a difficult task, just involved battery disconnection and some driving at various throttle levels or mentioned it at service and the dealers sorted it. but the car ran properly on 98RON. It hesitated at low revs on 95. ran lumpy.

the SLK200 didnt run any different whatsoever, on 98, 95 or supermarket fuels. so it go sainsburys stuff for 5p a litre less. no point wasting money.

the 55 is sorted to run on 98. am on optimax until i get used to the paramenters i drive at. then change will come to see whether it makes the differece. the dealer i got it from only use 95 in all their AMG models and have never had reported problems. MB recommend 98 for them.

i did run it on ultimate (97) for about 800 miles. but as the car has only done 1615miles so far I am not fully used to how it performs. will post when i have some better knowlege.

 

[c320]

I try to fill up with optimax at least once or maybe twice a month.

It maybe a placebo affect but after a few miles, you do feel a smoother drive, smoother acceleration so why not? The only thing that riles me is the cost which is why i only use it once or twice a month.

If like me you use your car for short distances, then you need to open the car up on a motorway once every now and then and give it a good old run and let her breathe!!

Just my opinion.

 

[malcolm E53 AMG]

Tried ASDA diesel and saved 5% on price at the pumps and lost 10% in mpg on the road in my 320CDi. Use Shell all the time and the performance is excellent, the engine runs smoothly and cleaner. The last thing I want is fuel system problems caused by diesel that burns less efficently. Goodness knows what effect cheaper diesel has on the nice fully synthetic engine oil we are all encouraged to use nowadays.

 

[turnipsock]

http://www.bp.com/sectiongenericarticle.do?categoryId=4005564&contentId=7009015

here's some clips to watch.