95 or 98 fuel

Unless its been tuned to run on 95 or 98, just run it on std 91 ulp?

fuel guide

fuel guide

Several things about E10 vs 91 RON petrol.
1 The energy content of E10 is less than unleaded petrol, so to get the same amount of power out of the engine you will need more of it. I have run tests on my wife's Mitsubishi Outlander, and I have found that I need about 10% more E10 to cover the same distance as if it was using 91 unleaded.
2 The RON rating is a measure of the anti-knock properties of the fuel. Whilst E10 may have a higher RON number, if your car will run OK on 91, you don't need any higher RON, so E10 offers no real advantage.
3 The altitude you are running at makes a big difference to the RON level of petrol required to prevent detonation or pinging. The higher the altitude, the lower the RON needed.
4 Some engines have a detonation (or knock) sensor built into the engine control. This allows the ignition to be advanced more with a higher RON fuel. The greater the ignition advance, the better the power delivery. Or rather, you can use a lower RON fuel but you will get slightly less power from the engine. I have tried running my wife's Outlander on 98 RON fuel and because it has a knock sensor, it did use less fuel for the same distance travelled. However, the extra cost of the fuel was not offset by the extra economy, and 91 RON fuel is still the most economical for us.
If your engine does not have a knock sensor, there is no point in using a higher RON fuel than specified unless you advance the ignition to take advantage of the better fuel. In modern engines, the ignition advance is set by the ECU, and rarely can you alter it.
I keep records of everything which goes into the car - oil, tyres petrol, filters etc and by far the largest cost associated with running a car is depreciation. Petrol comes in a long second.
The biggest factor influencing the fuel consumption is the deriving style. If you drive the car 5 km to the shops and back, the fuel consumption will be 50% or more higher than if you get the car warmed up and drive out on the highway at the normal highway speeds. Excessive acceleration or high speeds will chew up more fuel that anything else. My wife's car is used as a shopping cart during the week, so fuel consumption is awful, but regularly it gets used to drive 120 km trips (minimum) and you are then comparing maybe a week's usage of short trips - say 25 km - to 120 km of nearly ideal operating conditions. Our cars get much better operating conditions than most city cars.
As an example, some time back, I drove my car (a Pajero diesel, towing my caravan down) to Sydney. Highway speeds all the way, it used 11.1 L/100 km. Excellent, considering the caravan has the aerodynamics of a brick. My wife got sick and was in hospital for 10 days in Sydney. travelling each day from where we were parked to the hospital, I covered about 350 km, but used 13.3 L/100 km, and that was WITHOUT the caravan. Lovely thick city traffic. We were glad to be out of the place. Driving a petrol car in heavy city traffic will completely negate and fuel savings you can achieve by using different grades of petrol.

I am not sure if the Toyota engine has a knock sensor (from memory ti doesn't), but if it doesn't there is little value in going to the dearer fuel.

Philip L4 - What make of engine (there's more than one make of 4500cc size engine), and why do you ask?
Are you experiencing engine pinging, are you looking for more power, are you looking for more economy, or are you just curious about the economics of using either grade of fuel?

Cheers, Ron.

What does the owners manual say?

Sorry Phillip L4, you need to be less cryptic with your question. What vehicle are you referring to, how old, etc. Most modern European high performance petrol engines are designed to run on 95 RON.

Macca.

England an europe only have have 95 fuel
They don.t have 91
Mechpete

I used to frequently drive from central Vic to Adelaide/return. I first tried 98 in a 2008 2.2L Camry which used 10 litres less in 609 km, repeated many times, than lower octane fuel would deliver. 55L down to 45L used for 609km.
Changed to 1.8 Corolla and tried the same thing on exactly the same route both ways. First a few times with 95 and then with 98. The Corolla used less but not as much difference.
The Camry at the time returned a total money saving of about $4 even though the fuel cost more initially. Corolla only a small saving of close to $2.
Haven't tried it in a large petrol multivalve, but it may make a difference and cost less overall. Only your driving style and state of tune can ensure anything positive though.

$$$$ or Milage / Km should be the 'real' question ....My 4lt v6 by the 'book' is 95 ron or E10 is as well suitable , but here's the real thing , 159lt tank [ 014 Fj Cruiser ] low fuel light activates when 19lt left in tank ......91 ron consistent get 1,350km for 140 lt , when I use 95 ron get 1,390 for 140 lt and when have used 98 ron get 1,400 km for 140 lt .... there it is , no ifs , no buts ....price difference from 91 to 95 [on average out our way ] means to use 98 costs $30 more to do an extra 40km and an 'extra' $50 to do 50km more on 98 compared to 91 .... thats a lot of $$$$ over the 'life' of a vehicles ownership ....

We had a toyota dealer recommend using BP 98 few years ago how for our uzj v8 petrol landcruiser. while we no longer use the BP we still use 98 ~ hoping it runs better . Not cheaper ! But more ks to a tank full & cleaner motor ? .
350,000 ks & doesn't use a drop of oil .the dealer said it would take a few tanks of fuel b4 u notice much change , we think its worth the extra $$$ paid .