Thread: A P38s' preferable octane

So the difference in economy at 10.1% is less than the % difference in price as long as you are not in the boondocks where you cannot get 98 anyway.
Motormouth today prices in Northern Beaches of Sydney ULP 147.9, PULP 98 161.9, E10 145.9
Those prices are at the top of the cycle . Drop 10c off at say 137.9 and 151.9 and the difference is just about exactly 10%. Get your coles/woolies discount and the percentage will be more.

BTW , IMHO one trip is a little short a distance to compare, and I doubt that the real difference is 10% in economy in an 8.36:1 car unless of course it has a lot of carbon in it.
Regards Philip A

We had a Hyundai Santa Fe. It always ran better on 95/98 octane fuel. Went an extra 50-70 kms per tank. May not have balanced out the extra cost but in my mind well worth the cost. On 91 engine was rough on hard acceleration ( possible pinging ) , not there on the 95. There are also extra additives in the higher octane fuels to clean injectors etc. Even if not convinced of the benifits of 95/98 fuel all the time. Its a good idea to run a tank full every 4 or 5 fills

Gary

Originally Posted by benji

I was of the impression that all p38s were LR approved to run E10? I personally wouldn't touch the stuff, but if I was travelling and it was all they had it's nice to know it'll run on the stuff.

Also, many 'performance' chips require 95 or greater, this just means that when I do the cape, fraser, or simo etc. i've got to carry an octane booster.

In RAVE it states that low compression is 8.23, but on my block (i've just checked it) it also states 8.36.

on the contrary, LR specifically states not to use ethanol blends- there was a TSB about it. Ethanol can cause problems with the fuel gauge sender resulting in a deterioration of the variable resistor. A deposit builds up on the sender causing the gauge to indicate the tank is only half full even when the tank is topped up to the limit.... I have had experience of this having inadvertently filled up twice with bodgy fuel .... took ages and several doses of efi cleaner to get rid of the problem

Originally Posted by PhilipA

So the difference in economy at 10.1% is less than the % difference in price as long as you are not in the boondocks where you cannot get 98 anyway.
Motormouth today prices in Northern Beaches of Sydney ULP 147.9, PULP 98 161.9, E10 145.9
Those prices are at the top of the cycle . Drop 10c off at say 137.9 and 151.9 and the difference is just about exactly 10%. Get your coles/woolies discount and the percentage will be more.

BTW , IMHO one trip is a little short a distance to compare, and I doubt that the real difference is 10% in economy in an 8.36:1 car unless of course it has a lot of carbon in it.
Regards Philip A

Actually I considered a return trip of 3,100 km with a mix of city and highway driving each for each "event" was quite a reasonable sample for comparison purposes!

Originally Posted by Hoges

on the contrary, LR specifically states not to use ethanol blends- there was a TSB about it. Ethanol can cause problems with the fuel gauge sender resulting in a deterioration of the variable resistor. A deposit builds up on the sender causing the gauge to indicate the tank is only half full even when the tank is topped up to the limit.... I have had experience of this having inadvertently filled up twice with bodgy fuel .... took ages and several doses of efi cleaner to get rid of the problem

I've got a similar problem with my fuel gauge also where it doesn't show the maximum full, more like 3/4 full, but is slowly getting better after adding a regular dose of efi cleaner. According to the VACC wedsite all petrol LR products can run on E10, however as a rule of thumb in my opinion any vehicle regardless of brand built before the year 2000 should not use E10 as cars were never built with the intention of ever running on it, mainly cause it didn't exist (in Australia anyway!!). I ran mine on 95 octane for a while with the added benefit of slightly extra power, smoother & more responsive running, but didn't really get that much extra KM's out of it so returned back to standard 91 octane. I think the low comp motor will run comfortably on both 91 & 95 octane, 98 octane is just a waste of money as there was virtually no difference at all between that and the 95 octane.

...They need to be very selective about which petrol engines are suitable...

Re. low compression engines etc ...my nephew has done a beautiful job of restoring a 1928 Chev (CR less than 5:1 !). He rebuilt the engine without needing to change the valve seats etc to cope with unleaded or add a lead replacement because he discovered that it runs perfectly well on Shell 98 octane will no ill effects... tells me that his old car club mates discovered this some years ago when Shell first brought out its Optimax brand

Originally Posted by Hoges

...They need to be very selective about which petrol engines are suitable...

Re. low compression engines etc ...my nephew has done a beautiful job of restoring a 1928 Chev (CR less than 5:1 !). He rebuilt the engine without needing to change the valve seats etc to cope with unleaded or add a lead replacement because he discovered that it runs perfectly well on Shell 98 octane will no ill effects... tells me that his old car club mates discovered this some years ago when Shell first brought out its Optimax brand

Yes, but you do realise that the lead in the old Super petrol is a form of lubrication, though the engine may run OK on the 98 octane the net effect of not having any form of lubricity on the valve stem will create long term problems in premature valve wear. My mate found out the Hard way when his Camaro with the 327 V8 didn't last more than 58,000 km due to not putting lead replacement additive or some form of a upper cylinder lubrication system. He had the hardened valve seats, but still wore through it quicker than normal. Also important with a newly rebuilt classic motor is to use the best quality oil within a reasonable price preferably synthetic, and these engines will last forever.

I have discovered that mine is an 8.23 low compression so having read the other posts (thanks all for your replies) it would seem that 91 or 95 will suffice and there is little point in running on 98? Are there no benifits at all from running on 98? Lubrication or perhaps performance?