Petrol additives

Stephanie Plum · Post by **Stephanie Plum** » Sat Mar 12, 2016 6:36 pm

Hi folks
Can anyone recommend an additive for times when I can't buy a decent octane level superplus fuel? I put BP in today which is 97 and my old girl wasn't keen. I plan to run her down to a quarter tank tomorrow and get it filled up with 99 again, but I'm thinking that a bottle of additive would be useful to have in the car.
Cheers :)

Post by **Heuer** » Sat Mar 12, 2016 7:29 pm

My OTS has a 9.5:1 CR and runs happily on BP Ultimate 97 RON. Sounds to me your ignition timing is out.

Stephanie Plum · Post by **Stephanie Plum** » Sat Mar 12, 2016 9:43 pm

Mmm ok thank you. I'll test the fuel theory and then get that checked. I figure a tank of 99 is an easy test and something I can do tomorrow, and then get on the blower on Monday if she still hesitates.

Is it a complicated job?

Post by **Heuer** » Sun Mar 13, 2016 3:27 am

Set the timing up with 97RON, anything above that is a bonus. Alternative is to use a 123 dizzy with selectable maps for different fuel types. Sounds to me the ignition is too far advanced. Make sure you have the correct Factory specified plugs. Additives do work but they are hugely expensive and it means carrying a box of the stuff wherever you go which should not be necessary.

christopher storey · Post by **christopher storey** » Sun Mar 13, 2016 9:04 am

When is the pinking occurring ? If it is in the 1800 - 2500 rpm range it is a very common feature, and may be caused by slightly weak mixture at part throttle , or by the distributor advance springs being tired and allowing more advance at low to medium speeds than is required . It is a good idea to test the advance curve with a strobe ( vacuum disconnected )

cactusman · Post by **cactusman** » Sun Mar 13, 2016 9:20 am

I uses castrol valvemaster plus in my 3.8.....more for the (supposed) lead replacement additives rather than octane boost - seems fine although I agree with the other posts....get the timing right rather than rely on additives. I use super UL in mine but she runs OK on std 97RON when super is not available.

Stephanie Plum · Post by **Stephanie Plum** » Sun Mar 13, 2016 9:35 am

Thanks all. Pinking is at low revs but yesterday there was a hesitancy and stuttering when at lower revs in fourth, which was solved by changing to third and accelerating through it.

This is only the third time I have driven the car as it was tucked up through all the rain and salt of the winter, so I am still learning what it does.

malcolm · Post by **malcolm** » Sun Mar 13, 2016 10:35 am

Sounds more like a general tuning and set up issue to me as well Stephanie. I use 99 octane where I can, Tesco momentum works really well and is cheaper than Shell, but my car happily runs on BP97. In Spain I had to use 95 a couple of times and it was fine.
I'd tweak the timing back until it just doesn't pink and see how it is.

mark10337 · Post by **mark10337** » Sun Mar 13, 2016 2:35 pm

I use 95 most of the time - it's my daily driver and I'm not noticing any issues.

Stephanie Plum · Post by **Stephanie Plum** » Sun Mar 13, 2016 5:49 pm

We managed 130 miles today and topped up twice with Optimax and noticed a definite improvement, but I will defo get the timing looked at.

However, we had a slight drama when we got home which will need more immediate fixing, but I'll start another thread rather than clutter this one.

Thanks everyone for the input :)

Paul71a · Post by **Paul71a** » Sun Mar 13, 2016 7:27 pm

Are you sure you're firing on all cylinders?

I got mine out for the first time yesterday since it's winter layup and it drove like a dog!

On listening it was missing..... Took about all the plugs and gave them a clean......

Drove wonderfully after; usual issue with starting up over winter without giving it a good blast.... My Seven used to have the same issue..

cactusman · Post by **cactusman** » Sun Mar 13, 2016 9:34 pm

Sounds like a tune of those carbs would be wise. Brimmed mine with good old Saintsbury's super at ?1.05 and a splash of castrol additive.. Goes like a train and pulls from 15 mph in fourth. If you have triple SU carbs make sure all three needles are correctly set in the pistons and the pistons move unhindered. Just a couple of mm difference between one needle and another makes a a MASSIVE difference and will make it impossible to set them up....I know!!!!!

Stephanie Plum · Post by **Stephanie Plum** » Wed Mar 23, 2016 5:04 pm

Sorted today. All carbs were tuned, plus the distributor, plugs, leads etc were all checked to be sure. The journey home was a sweet one.

Thanks to everyone for their input. I'm learning all the time.

Must say a big thanks to Grahame Bull of CMS who spent 3 hrs on the car this morning sorting some bits and pieces out for me, which were inevitably going to arise with a car that hasn't done much for the last 8-10 years. All foc and teaching me what he was doing as we went along. Great guy - can thoroughly recommend him.

Paul71a · Post by **Paul71a** » Wed Mar 23, 2016 5:37 pm

Graham is a star; his wife keeps her horse at the same stables as Paula. He has a reputation as a reasonable, fair man; quite a task for a car dealer!

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