95 or 98 petrol - what do you use?

[tigger73]

Totally agree. However, if I get better MPG (L/100KM) using the 95, I'll use the 95. You might have guessed from the fact I was running V8s and now a Duke the cost of fuel does not concern me. The only proviso is I match or better the minimum fuel requirement...

I've logged my car to look at how much timing retardation the ECU is pulling. I've then had the ECU retuned to operate safely on the fuel I'm running. In this case it's Caltex Vortex98 which in SA is definitely not the same as other 98 octane fuel on the market. Generally the manufacturers will put in a tolerance for poor quality fuel in the ECU, however like I said the ECU can only pull timing so far before you get detonation (typically only around 5 degrees).

[theresanothersteve]

It will only pull timing so far before you get detonation.

If your car specifies min 95 then I guess it's up to you. To be safe I'd always run on the higher octane fuel.

It's not a question of fuel efficiency and whether you can save 0.01c per km, it's about engine life which could potentially cost $1,000's to repair.

Here's something else...

You'll notice from my signature I also run a Ducati. I switched from 95 to 98 to see if there was any difference. Fuel consumption remained the same.

I began to develop a starting issue. Instead of first pop it was taking at least three attempts to get it going. I spoke to the dealer and he suggested to bring it back and they'll put on the latest computer updates, supposedly one was related to fuel mapping. And yes, others were reporting starting issues.

In the mean time I switched back to 95. And the starting issue disappeared.

The moral? Run the minimum fuel standard from thew owner's manual. Try fuel that exceeds the minimum requirement, but monitor the results. If you don't get better fuel consumption or performance (consumption is easier to measure than performance and as the two are related to engine efficiency is probably a good indicator) go back to the 95.

[h100vw]

We measured ran a MK7R on our dyno, made 155kw atw. Nearly 20kw down on the average we see. Owner fessed up to using 95. He was in to get a stage 1 tune, we had to send him away and run through a few tanks of 98.

Different demographic for sure, but if your ecu advances the timing and makes more power, you need less throttle input for the same progress. Noting fuel consumption around town wont really give you the best look at how the fuel makes a difference.

[Ozsko]

We measured ran a MK7R on our dyno, made 155kw atw. Nearly 20kw down on the average we see. Owner fessed up to using 95. He was in to get a stage 1 tune, we had to send him away and run through a few tanks of 98.

Different demographic for sure, but if your ecu advances the timing and makes more power, you need less throttle input for the same progress. Noting fuel consumption around town wont really give you the best look at how the fuel makes a difference.

When he brought it back it was up 20kw?

[Pzero]

Switched from 98 to 95.
Noticed no difference in performance or drive.
Consumption is similar or better.
Sticking with 95.

[aprr32]

The slower it burns the better the power-longer push on the piston with more timing.

[adrianb]

Always run 98 in my FGX XR8 Falcon and in the wife's Tiguan. I prefer BP Ultimate but I couldn't put anything remotely scientific behind why.

[ewok666]

Always run 98 in my FGX XR8 Falcon and in the wife's Tiguan. I prefer BP Ultimate but I couldn't put anything remotely scientific behind why.

Got a tuned Tiguan so would be stupid to run anything other than BP98. Without the tune any decent 95 souls do the job but who knows. In anticipation of the tune we always filled up with 98. I would never NOT tune a car when the results are that good!

[FastMitch]

I know this is not part of the OP original Q, but has anyone used Unleaded 91 in a new 17/18 Tiguan with no reported issues ?

[theresanothersteve]

I know this is not part of the OP original Q, but has anyone used Unleaded 91 in a new 17/18 Tiguan with no reported issues ?

Don't do it. Just don't.
Many of the reliability issues with the twincharged motor came about because people were using 91RON.
If you use 91 there is an increased chance of detonation or preignition. It's not like an old red motor Holden that, if it started pininging, you'd call in the local servo and a mechanic would check your timing (yes, I'm that old). You might not even be aware its happening as the ECU tries to accommodate the fuel. But it's doing damage inside the motor.
Why buy a vehicle because it offers good, smooth performance, and compromise on that to save a few cents a litre?