Mk1 Ls400 Fuel Grades

[Malc1]

Does anyone else have a Mk1 ?

I've religiously refilled my Mk3 on E5

and yesterday my " new " Mk1  ......  the manual for this car says tank capacity 85 ltrs, the orange light emerged at 75.42 ltrs to refuel  .....  no problem there, usually 100 miles left in the Mk3 tank ok

BUT reading the Official 1991 Ls400 Manual I'm reading it says  min 95 octane fuel ( where possible ) 

NOW then , for this specific 1991 car with all the differences with both this car technology compared to a later Ls400 AND the manifest changes to fuel in itself ....  should I be reverting to simple E10  95 octane ?

Your thoughts please

Thank you

Malc

[ambermarine]

As far as I can tell through research the Mark 4 ls 400 is the only model of the Lexus ls400 range that can safely use E10 .My research from various sources cites detrimental to fuel lines and engine in previous models due too excessive h2o content in E10 which suggests Lexus changed the system on the Mark 4 in anticipation of these changes in the fuel content .

I have tried E10 and premium in the car I have and my experience is that the performance and mpg are down significantly when I use E10 but there are no issues with the mechanics of the car.

[BigBoomer]

Don't confuse the E5/E10 with the Octane number. They have quite different meanings.

E5/E10 relates to how much Ethanol is in the petrol.
E5 = up to 5% Ethanol.
E10 = 5% to 10% Ethanol.

The Octane rating is a measure of how resistant to knocking that fuel is in engines. In the UK/EU we use Research Octane Number (RON).
If you can get E5 95RON then that is safe to use in your car, but you need to avoid regular use of E10 regardless of the RON.
Since almost all 95RON is now E10, you should stick with E5 96-99RON.

If for some reason you can only get E10, then the garage will have some E10 Additive that you need to add to the tank to prevent damage.
However, if it is only for one tankful and the car is not going to be standing for a long time with the E10 in it, just use it.

[Malc1]

Thank you Phil and George, yes I had forgotten about the degradation in the pump fuel itself and the potential long term harm to fuel lines etc with added water / ethanol etc in the fuel itself  ......  95 octane fuel has been buggered about with and it's just the new E5 that's as best as it can get for us old Ls400 laggards 

I'll stick to the E5  and make sure I use a tankful in each of my cars every couple of weeks eh !     I wish 😅

Thank you

Malc