Supermarket petrol (again)

HardRockCamaro · August 08, 2007, 11:38:50 AM

Not in the news, this is my experience.

I was away in North Wales this past week and while I was there I noticed petrol was a bit pricier than in London (surprisingly) so I decided to take advatage of Tescos petrol pricing. I have done so occasionally back in London.

The Caddy always gets super unleaded, so 97RON or better. Tesco's super (Finest?) is a whopping 99RON so that's what I use.

Turns out the Caddy doesn't seem to like it at all.

She idles *very* rough from cold and fails to fire on a hot start forcing me to give the throttle a good few jabs to bring her to life (normally no throttle needed).

I tried two tank fulls of Tesco 99RON from 2 different petrol stations (in case of water in a tank at one store) and the result was the same. I filled up with Texaco 95RON afterwards and those problems went away.

I have had some hot start problems in London a couple of weeks ago and I'm pretty sure it was a tank of Tesco fuel at the time. I had also had a problem with the car running rougher than ususal so I changed all the spark plugs (the car has only done 34,000 miles and the platinum plugs can supposedly last 100,000 miles) even though they looked ok. It made no difference.

But switching to regular brand fuel seems to have solved the problem...

I know Tesco 99RON is actually E5 fuel (95% petrol, 5% ethanol) and maybe that's why the Caddy doesn't like it?

Cunning Plan · August 08, 2007, 12:33:10 PM

Quoting: HardRockCamaro

I know Tesco 99RON is actually E5 fuel (95% petrol, 5% ethanol) and maybe that's why the Caddy doesn't like it?

Makes you wonder what their normal stuff is

sixpack2639 · August 08, 2007, 12:43:42 PM

The engine in your Caddie is designed to run on the lower grade fuel mate. If you put higher than recommended in it the computer gets fouled up and doesn't know what to do so it leans the mix too much thus your hard start problem and rough idle.

Hope that helps, Carl

HardRockCamaro · August 08, 2007, 02:04:13 PM

Cheers Carl.

I know that 2000 was a changeover year for the Northstar engine, you had to put premium in up to that point, then regular was allowed from some point in 2000 on. At the same time they switched to coil on plug.
Mine is a 2000 but it's a 1999 build and doesn't have coil on plug, instead it has 4 coils. The gas cap says premium only so I order parts as if it were a 1999 model.
Now, we call our cheap stuff "premium" and the good stuff "super". So in thoery the cheap stuff is fine but I'm a bit cautious as there could be a different meaning over here. I know that our 95 and 97/98 are not the same numbers as your 92/93 or whatever, ie they're not "better". It's really confusing actually.

The car runs great on 97 or 98 "super" from Texaco, BP, Shell or Esso. It's only Tesco "super" which is 99 that it doesn't like. Tesco were in the news a few months ago over this particular fuel, it destroyed the o2 sensors on many cars.

I think I'll just stick to the name brand fuel and maybe try Tesco 95 fuel if I get caught out.

Flip Martian · August 08, 2007, 03:07:07 PM

I've been running my 1999 Camaro V8 (not the same engine I know) on Tesco 95 and it runs very nicely. There's a label on the filler cap that says "Premium" but I took the advice of someone else who said the basic stuff was fine for the LS1 engine.

Pod · August 08, 2007, 03:51:58 PM

I bung Tesco Finest petrol in my car. Have done for quite a while now.
The main reason is that Tesco's is right next door to us and the finest is only a couple of pence per litre more so I figured why not.

I tried a few different ones a while back and to be honest didn't notice any difference with any of them. So it's just the easiest one to get to now.

ianjpage · August 08, 2007, 05:06:32 PM

tend to use sainsburys petrol as (a) its the cheapest around (b) i get nectar points and (c) its nothing more than unbranded BP fuel....never had a problem or noticed any difference when put "branded" esso/bp/shell stuff in

sixpack2639 · August 08, 2007, 05:38:24 PM

Our gasoline grades are as follows.....

Regular Unleaded is generally 85-88 octane.

Super Unleaded is generally 89-91 octane.

Premium Unleaded is generally 92-96 octane.

I'm sure our octane rateings are a bit different from yours though.

I have a similar problem with my carbureted 1981 Olds as far as brands goes.

On Enmark (which is usually the lowest priced gas around) my car runs shite. On Shell, Hess, BP, or Exxon she runs just fine so the only thing I can assume is the Enmark is an inferior product.

Titsy · August 08, 2007, 06:43:42 PM

Quoting: sixpack2639

I'm sure our octane rateings are a bit different from yours though.

You guys use a Motor / Research Octane Number Average. The difference between the two is generally about 10. So to equate a US pump rating to a UK rating you ad on 5 and that's about right.

Quoting: Flip Martian

I've been running my 1999 Camaro V8 (not the same engine I know) on Tesco 95 and it runs very nicely.

You'll probably find it's more economical on your wallet to run super. by running regular in an LS1 you'll constantly be running retarded ignition to stop any knock, this equates to les useful energy being produced from the burned fuel. And so less miles per gallon and more importantly, less horses per bang...

Even on my LT1 I found that my pence per mile was better when I filled up on super than on regular.

Roadkill · August 08, 2007, 06:47:57 PM

Quoting: sixpack2639

Our gasoline grades are as follows.....

Regular Unleaded is generally 85-88 octane.

That's poor.

I run all of mine on BP regular . . . When the Caddy's done she'll get Super.

Titsy · August 08, 2007, 06:52:36 PM

Quoting: Roadkill

That's poor

Quoting: Titsy

You guys use a Motor / Research Octane Number Average. The difference between the two is generally about 10. So to equate a US pump rating to a UK rating you ad on 5 and that's about right.

So that's 90 - 93 by our standards.... I don't think i've seen anything below 95 in the UK, but then they tend to have lower compression engines in the states...

Flip Martian · August 09, 2007, 04:14:29 AM

Quoting: Titsy

You'll probably find it's more economical on your wallet to run super. by running regular in an LS1 you'll constantly be running retarded ignition to stop any knock, this equates to les useful energy being produced from the burned fuel. And so less miles per gallon and more importantly, less horses per bang...

Even on my LT1 I found that my pence per mile was better when I filled up on super than on regular.

Thanks mate - I'll give that a go next time I fill up then!

HardRockCamaro · August 09, 2007, 07:32:43 AM

The Caddy gives better fuel consumption on super, about 2mpg or so.

I think the IROC does too although I've not been too scientific about the tests on that.

philoldsmobile · August 09, 2007, 03:34:30 PM

the stang returned slightly better MPG on BP ultimate (best of 36.1) but the price difference simply didn't justify it..

there was no performance difference