Super Unleaded....Advice needed

[merc180k]

What are the advantages/disadvantages of running your car on super unleaded?

I've heard various horror stories and need some advice.

Thanks

 

[recycled]

What horror stories. i have heard none yet

 

[Bobby Dazzler]

If your ECU can adapt to the higher octane rating offered by super unleaded fuel then your engine can potentially produce more power. The biggest benefits are seen on modern relatively powerful turbocharged engines.

The higher the octane rating then the greater the potential benefit, ie 99 RON V-Power or Tesco Super has greater potential than 97 RON Super Unleaded.

Not much more to say really.

 

[Ian B Walker]

It rather depends on how old your engine is. I have heard that a now and again fill with Optimax or similar is ok, but prolonged use can burn the pistons. Its not gospel, just what I have heard.

 

[recycled]

just read your handbook and fill up with what it says 95 ron /97 ron whatever. Same as oil or bulbs really

 

[merc180k]

That it can damage the engine if used for long periods, that it can cause damage to the knompressor etc. Although I also know someone with a Subaru who was told to use nothing else because that would damage the engine and they have used super unleaded for 6 months or so.

I just don't know what the best option is.

 

[recycled]

Well some cars like the bonkers evo9 fq400 can only run on shell optimax
probably a shell marketing ploy.
Imagine if shell became an auto maker and had the market like the microsoft /netscape fiasco?
They would make sure all fuel sold can only run on shell cars GTi so everyone would have to ditch the merc and buy a shell car.
Like ditch netscape navigator and get IE as netscape was not running on windows
Sneaky and spoooooooooooky

 

[BTB 500]

I posted some info. on benefits yesterday:

http://www.mbclub.co.uk/forums/showpost.php?p=377301&postcount=8

With the current "claim culture" I doubt the oil companies would risk selling fuel that had the potential to cause engine damage.

 

[Carrotchomper]

My mum used to run a BMW 5-series in the early nineties when unleaded was starting to make much more of an appearance. She always used to be somewhat of a luddite and was concerned about the cost of "converting" to UL. Ran her car for a good 2 years before biting the bullet and going to a garage- Who promptly told her she could have been running on the far-cheaper unleaded fuel all along! D'oh! And before ANYONE starts, performance is not an issue!

 

[Dieselman]

Unleaded

Pretty well any car with an aluminium cylinder head could take unleaded as they had to have valve seat inserts anyway.

Mind you I used to run my Sierra on it and that was definately not designed for it..but...it didn't seem to do any damage...well not short term..

 

[big x]

What are the advantages/disadvantages of running your car on super unleaded?

I've heard various horror stories and need some advice.

Thanks

With my BMW I get better MPG and slightly better performance using V-max.
I did a double blind test to check it wasn't my imagination. Got a friend to fill the car up 4 times without me knowing if it was 95 or 99 octane and I called it right every time.
The handbook does state the car gives better MPG and performance with 98 octane over 95 or 92 the lowest recommended.
To understand octane read this http://en.wikipedia.org/wiki/Octane_rating
Perhaps the biggest benefit of using a premium fuel is they have better additive packages, I've certainly seen independent tests showing valves and pistons run cleaner.

adam

 

[MangoMan]

All I can say is, is that I have been using S/U in my Toyota since I can't remember, what, 5-6 years now, and in all my Mercs the last 4 years. No ill affects so far, other than increased performance.

 

[Glenn Smith]

A fuel with a higher octane will not cause any damage, it will allow an engine to run with a higher ignition advance due to it's higher knock resistance, a modern petrol engine uses knock sensors, these retard the ignition at the onset of knock, so the engine always runs at the optimum ignition advance, the super should see knock happening at a bigger advance, a high performance engine is likely to see more benefit, high compression and forced induction engines will knock (or pink) earlier neccetating an early retard of ignition advance. I accidently put some in mine in Germany the other week as they use a ROZ rating which 95 is equal to about 98, didn't really notice a differance untill i put ordinary back in, i was fully loaded at the time and the car did feel slightly less eager.
I will use a higher octane if the price is very close to normal. I don't know if i could measure the gain in mpg as we don't monitor that closely and journeys are not the same every week.

 

[amwebby]

I've just had the reverse experience. My 2000 CL500 kept running rough after rapid acceleration, a fault that could only be cured by turning the engine off, thus resetting the ECU and it was highly likely to do it again the next time the pedal was pushed to engage 2nd kickdown. I had determined it was the MAS and was preparing to replace it at the next service,which is nearly due.

Then a friend, who works at a major oil company, told me not to waste my money on premium unleaded, it was all marketing. so I switched to regular. I've been running on that for 4 tankfuls now. I haven't noticed any decrease in performance but the rough running problem has disappeared. Concerted attempts to replicate the problem have failed.

 

[BTB 500]

I've just had the reverse experience. My 2000 CL500 kept running rough after rapid acceleration, a fault that could only be cured by turning the engine off, thus resetting the ECU and it was highly likely to do it again the next time the pedal was pushed to engage 2nd kickdown. I had determined it was the MAS and was preparing to replace it at the next service,which is nearly due.

Then a friend, who works at a major oil company, told me not to waste my money on premium unleaded, it was all marketing. so I switched to regular. I've been running on that for 4 tankfuls now. I haven't noticed any decrease in performance but the rough running problem has disappeared. Concerted attempts to replicate the problem have failed.

I've always run my R129 on Optimax and then V-Power, with no problems whatsoever.

As already mentioned, the premium fuels will give limited benefit in low-tuned cars but are definitely not "all marketing". The increased torque is clearly noticeable in my Sharan when I'm using full power towing the caravan. The 5th Gear test I posted a link to above measured bhp and torque increases on a dyno. Dynos aren't normally affected by marketing

 

[amwebby]

I've always run my R129 on Optimax and then V-Power, with no problems whatsoever.

As already mentioned, the premium fuels will give limited benefit in low-tuned cars but are definitely not "all marketing". The increased torque is clearly noticeable in my Sharan when I'm using full power towing the caravan. The 5th Gear test I posted a link to above measured bhp and torque increases on a dyno. Dynos aren't normally affected by marketing

I agree and I'm not entirely convinced by my friend's scepticism. Nor am I absolutely sure I haven't lost some degree of torque, on the CL500 it is hard to tell, even when running rough, as described earlier, it will still out accelerate most other cars.

However, I am convinced that the switch to regular unleaded has 'solved' my supposed MAS problem. Anyone more technical than me care to comment on that?

 

[BlackC55]

If I put optimax in the Smart I get 240 miles to a tank. If I use regular unleaded I get 205 miles.

Same driving same roads etc.

 

[Bobby Dazzler]

However, I am convinced that the switch to regular unleaded has 'solved' my supposed MAS problem. Anyone more technical than me care to comment on that?

If you get your Super Unleaded from the same petrol station every time, maybe their tank is contaminated in some way?

 

[television]

My SL handbook says 95 for the 500 and 98 for the 600, I could not tell the difference between the two in my last SL320.

I have not tried super yet as the difference down here is 10p and it is not worth that

 

[BTB 500]

If I put optimax in the Smart I get 240 miles to a tank. If I use regular unleaded I get 205 miles.

Same driving same roads etc.

Yup I use V-Power in the Sharan when we drive to Stuttgart, for the same reason. The extra range makes the difference between just doing it with one fill-up en route (carefully juggling the 'miles remaining' on the trip computer with the TomTom distance to next petrol station!), and having fuel in reserve.