- DrTeeth
Modern engines are not optimised for 99 Octane fuel. They have to have anti-knock sensors that can dynamically advance the timing until pinking occurs and them slacken it off a bit. If they were indeed optimised for 99, they would pink like crazy on 95 and burn holes in the pistons as well as being very gutless and having atrocious fuel economy.
- B Whinnie
Regarding your comments to JC, where you recommend the new Mercedes-Benz GLC range, Not being financial able to buy a MB, I looked at your previous review of the 15 year, model GLC, rated 5 star, but with a long list of problems many of them on cars under 3 years old, furthermore poor dealership response, I suggest readers take a look at John Cadogan at autoexpert.au on YouTube, His name for MB's is "s*** Boxes", Say's it all!
- Miniman777

With regard to RS and his Nissan radio/sat nav issue, I understand there are many instances of this fault. I have a 65 plate (Oct) Juke which has done this since February. I've missed turnings because the nav has stopped speaking, had calls drop out and radio or streamed music ceases. Sometimes the sound returns, on other occasions, the unit reboots itself. Then I can go for weeks without a problem. As the car is due to be replaced in 6-8 weeks time, I am living with it, but it's a known and expensive problem.

I also find it odd there is no indie fix for the infotainment set either.

Edited by Miniman777 on 06/09/2019 at 22:30

Honest John's Motoring Agony Column 07-09-2019 Part 2 - MrPogle

"Optimised" does not mean "will only work with" it means "makes best use of". The fact that modern engines are optimised for 99RON does not mean they can't tolerate 95. It means that if 99 is available they will perform better.

Honest John's Motoring Agony Column 07-09-2019 Part 2 - misar

I have had a Mazda 3 with their 2.0L 150PS manual option (Sport), from new and now at around 32K miles. It has always run as recommended in the Mazda manual on branded 95 RON unleaded (mostly but not always BP). As an HJ fan I finally succumbed earlier this year, ran the tank low and refilled with 99 RON. It then had another four tanks of 99 RON, all BP, before I went back to 95 RON.

I honestly could not detect any difference in everyday performance - the car drives very well and felt exactly the same on both grades. More surprising, after reading HJ's comments for so long, the mpg was the same. I always keep a very detailed record (brimming the tank, not from the computer) and while on 99 RON mpg stayed almost identical to the long term average. I could actually see the consistency with each tankful because I always zero a mileage trip after each fill then look for the mileage at which the fuel gauge drops to half full. Not sure if it is Mazda or my driving but I have long been surprised at how good that is for guessing when the gauge is about to change (it has eight markers rather than a pointer).

Edited by misar on 08/09/2019 at 20:18

Honest John's Motoring Agony Column 07-09-2019 Part 2 - Engineer Andy

I have had a Mazda 3 with their 2.0L 150PS manual option (Sport), from new and now at around 32K miles. It has always run as recommended in the Mazda manual on branded 95 RON unleaded (mostly but not always BP). As an HJ fan I finally succumbed earlier this year, ran the tank low and refilled with 99 RON. It then had another four tanks of 99 RON, all BP, before I went back to 95 RON.

I honestly could not detect any difference in everyday performance - the car drives very well and felt exactly the same on both grades. More surprising, after reading HJ's comments for so long, the mpg was the same. I always keep a very detailed record (brimming the tank, not from the computer) and while on 99 RON mpg stayed almost identical to the long term average. I could actually see the consistency with each tankful because I always zero a mileage trip after each fill then look for the mileage at which the fuel gauge drops to half full. Not sure if it is Mazda or my driving but I have long been surprised at how good that is for guessing when the gauge is about to change (it has eight markers rather than a pointer).

It's OK Misar, you're not the only Mazda car owner who's found this. The mpg in my 1.6 petrol version went up by about 3-5%, essentially 2mpg, which could've been due to better traffic and weather conditions than before. Either way, I didn't notice any difference in actual performance.

What may make a difference is if the person changing uses branded fuels with more cleaning additives and if they use the car for mostly short trips from cold (not my driving pattern), so the cleaning effect makes the car run more smoothly on acceleration or get an mpg level more like when it was new.

I bet that the 2.3T MPS version would be optimised for higher octane fuels, but like most Japanese cars, it can easily get by with 95 RON.

- jchinuk
Re : Aston smarting
With all due respect, buying an AM and doing "less than 1,500 miles per annum" seems an uneconomic deal. Surely it would have been better to hire a suitable AM (probably a newer one) on a few occasions a year?
- daveyjp
I know an Aston owner, he accepts part of his annual running cost is a comprehensive AM warranty which is available for up to ten years.
 

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