Unleaded petrol....a youngin' question

Ibrox90 · 13-02-2011, 07:09 PM

Hey,

(forgive my ignorance)

So tomorrow I'm going to pick up a 75-77 Chrysler Sigma.

Now I assume that will run on straight 91 octane ULP

Or is it old enough to need an additive.

TheInterceptor · 13-02-2011, 07:10 PM

Yes it will run on 91, yes you need the additive to avoid valve head recession and other things that will shorten the life of the motor.

**aussiblue** · 13-02-2011, 07:35 PM

98 Ron maybe better (or worse). Experiment and see. My 1963 seems to like 98 Ron best while my 1980 lancer runs best on PULP (premium unleaded). Even different brands can perform differently and sometimes a 50:50 mix of Rons (swapping every second fill) can work best. I would ask at http://www.sigma-galant.com in the Sigma forum what others with similar cars or the identical engine find best. I also use an upper cylinder head lubricant in both (Red-X) and my 1980 LC Lancer that I have had since new (over 300,000 km) is still running fine and has never had its head off.

**Silver Ghia** · 13-02-2011, 07:54 PM

The leaded fuel available back in the '70's and early '80's was mainly 'Super' which was 97 octane minimum, so using BP ultimate (98 RON) is equivalent as far as octane rating is concerned (to avoid pinging). But since Ultimate is unleaded, it also needs the valve seat lubricant to avoid recession as mentioned.

For my pre unleaded cars I have used BP Ultimate with Penrite 'Valve Shield' additive available from Autobarn etc ever since Ultimate became available. The required amount of additive is poured into the fuel tank before filling with fuel, so it mixes in the tank as you fill up.

XCwillo · 13-02-2011, 07:59 PM

Dont use the 9 crap. Best to use 98 with lead additive.
I use BP Ultimate with Nulon Lead additive and my XC doesnt skip a beat.
Put 91 in and even with lead additive, it after fires when i turn the car off.

Zedjay · 13-02-2011, 08:12 PM

you dont need to add anything to it...most jap cars with alloy heads built in the 70s were built to run on unleaded..we were way behind when it came to switch to unleaded..

you could even run 91 or E10.. if it pings back the timming off a bit

edit. so i dont get flamed

http://www.aip.com.au/health/lead_guide.htm

ZA-289 · 13-02-2011, 10:32 PM

Its a sigma put in whatever you want!

I wouldn't bother about the additive unless your keeping the car for years and years..... it doesn't destroy the valves that quickly

Ibrox90 · 13-02-2011, 10:46 PM

I wont be putting, 98 in it thats for sure, the idea is to use it as a daily, and IF Idecide to keep it for longer than a year the chances of it staying a 4 cylinder will be very slim

XR6 Turbo motors are getting cheap these days

Mickxr8 · 13-02-2011, 10:47 PM

[QUOTE=Zedjay]you dont need to add anything to it...most jap cars with alloy heads built in the 70s were built to run on unleaded..we were way behind when it came to switch to unleaded..

you could even run 91 or E10.. if it pings back the timming off a bit

+ 1 ^

Ibrox90 · 13-02-2011, 10:51 PM

I now have some light reading which suggests that its fine to run on regular 91

XCwillo · 13-02-2011, 10:59 PM

Forget my post
I totally read Chrysler Valient in your original post cause i was talking to my mate about one at the time.
Then when i saw in others posts "Jap car" and "4 cyl" i was liek waaaiiiit a second! >.<

BradZ · 13-02-2011, 11:05 PM

My paddock bomb which is an 86 needs lead additive cause it ran on leaded fuel. I would assume the Sigma will need the same?

Road_Warrior · 14-02-2011, 12:07 AM

Quote:

Originally Posted by Zedjay

you dont need to add anything to it...most jap cars with alloy heads built in the 70s were built to run on unleaded..we were way behind when it came to switch to unleaded..

you could even run 91 or E10.. if it pings back the timming off a bit

edit. so i dont get flamed

http://www.aip.com.au/health/lead_guide.htm

+ 2

Talk about needing 'additives' is complete crap

As Zedjay said they were designed for it looooong before our poxy restrictions kicked in. In the US it was mandated from 1976!

**aussiblue** · 14-02-2011, 01:10 AM

Quote:

dont need to add anything to it...most jap cars with alloy heads built in the 70s were built to run on unleaded..we were way behind when it came to switch to unleaded..

Just remember that some OZ Mitsubishi engines were made in Australia and have some significant differences over North American, Japanese and European Mitisubishi engines. For example, most North American and Japanese engines of the late 70's had MCA (Mitsubishi Clean Air) air jet injection and cat converters that were not on the Australian equivalents. MCA involved air intake valve in each cylinder (called the jet valve) in addition to the intake and exhaust valves to create strong swirls for enabling super lean burn.
see http://www.jsae.or.jp/autotech/data_e/9-9e.html

Other smog and ULP devices on non OZ cars included more complex fuel vapour recirculation systems and more sophisicated EGR systems.

**aussiblue** · 14-02-2011, 01:14 AM

Zedjay · 14-02-2011, 02:45 AM

Quote:

Originally Posted by aussiblue

you can still run them on unleaded though.

edit; sorry i ment to quote the post above the one i quoted

Jimmyd · 14-02-2011, 01:05 PM

Sigma had an alloy head that came with hardened valve seats fitted from factory. No additive is required.

As its a daily flog box - if she pings on 91 just retard the ignition timing a little until it stops pinging.