Hydrocruiser

I am using 87 octane gasoline in one of the family vehicles; a Freestar Minivan. It has the new 3.9 L V-6 and is a great running car for the wife and family and for hauling things to the lake. One problem is that the engine is very sensitive to gasoline and hence knocking when on the freeway, especially when passing or doing 70 mph. I was using Shell 87 and it knocked really bad. So for a little while I went up to 89 and then Shell 92 and then no more knocking.

I then decided to take it to the Ford dealer and they checked it out and said to try a different gasoline brand. I was not very hopeful. I let the tank go dry and tried Mobil 87 and absolutely no more knocking. Later tried Sunoco 87 and back to knocking; Citgo and it knocks; BP/Amoco is a bit better. Marathon and Speedway 87 were decent but I swear that 87 Mobil is the best thing out there for this vehicle without upgrading.

I know some vehicles need more than 87 but let's limit this to 87 only.

So I decided to do a poll and see what you guys think.

Payton

Where are you? It may have something to do with if the gas has to have the oxigenator(sp) additive. I understand MTBE can cause a knock but Ethynal has less of a tendancy to knock, as it raises the octane rating a little.

David

Used to use Shell 87 in wife's car, but sometimes noticed excessive spark knock. Noticed a couple times, tanker truck was unmarked, like maybe not really Shell fuel? Switched to Exxon 87, sometimes knock, sometimes not. Doesn't seem to be dependant on which station we go to either.

bob_t

I have a 2001 Chevy 2500HD with the 6.0L motor. Everyone knows or should know how bad they suffer from pre-ignition (and ColdStartKnock, too, but that is different). Shell 87 doesn't ping constantly, Marathon 87 rarely pings, Mobil 87 pings occasionally, but BP 87 literally pings constantly (you should hear it if the A/C is on). It even pings on 89 octane and some 93 octane, more than you would ever expect any engine to ping at all, especially on higher grades of gas. Put the 9000 lb boat and trailer behind it and it really rocks! Just waiting for pieces to either blow out the bottom or put dents in the hood! All of this is even after having the recommended GM re-flash done to my ECM. That re-flash was an improvement for the pinging (it was unbelievable before the re-flash) but there was a noticable decrease in fuel economy and power/acceleration. It has been on several GM diognostic scanners and everything checks OK. This is not just my truck as many owners of this engine have complained about the pre-ignition, and it is a known problem. It is just aggrivated by the brand of gas!

scottsumrall

my truck is a 2500hd 6.0, and it does the same thing. i called gm and they said that this was normal and it would not hurt the motor, right, but they did give me a 100,000 mile warranty on the motor.

bob_t

I don't remember whether my "free" warranty was for 60,000 or 100,000 miles, but, they gave me an additional warranty, too. If I ever need it, I wonder if they already have a way to snake their way out of it. "Sorry, but we have no record of you changing the air in your tires as recommended, so your engine warranty is void"

Hydrocruiser

http://www.exxon.com/USA-English/Fil...p%20100102.pdf

Takes 5-10 seconds to open. It shows what gasoline you get in the areas where you live.

Gasoline with a Reid Vapor Pressure of 7.8 PSI is low it used to be 9.0+.

You Florida Southern Coast guys get this stuff too.

It costs a lot of extra money to refine and then we blame the Arabs for high prices. The air is clean enough; when will this nonsense ever end?

88Fount33

I have the old 454/330 with what feels like 5 to 1 compression so cow pixx works fine for me. I kinda don't like it when the marinas only sell the 89 grade.

Havasu Cig

FYI there is no more Union 76. Conoco Phillips owns the 76 brand. Being a Conoco dealer I am a little biased, but I believe you will not find a better quality product out there.

Conoco did some testing on different blends from the various companies and the result was Conoco's blend was the highest quality with Chevron a close second.

I know when I have been forced to run Arco gas in the boat in the past I found the transom was very black at the end of the day. When I have run Conoco or Chevron gas this does not happen.

Different parts of the country will have different blends as well.

Thunderstruck

Guys you are not necessarily getting gasoline from the refinery that brands the gasoline at the station. The nasty little known fact is that depending on where you live, gasoline distributors buy gas from a pipeline and as long as it meets the specs it goes to the station. Otherwise an Exxon station and a Shell station across the street from each other could not compete with each other depending on who had the closest refinery. Specs include RVP, octane, corrosion rates etc.

Now, what is done at the terminal is to add the specific brand's additives i.e. Techron for Chevron, etc. but that is for detergents/antioxidants not octane. Sometimes refiners trade/buy or use their own out of spec gasoline to blend octane or whatever down because they don't want to "give away" octane i.e. they want to hit the 87 and not one tenth above 87. But, I really suspect that some out of spec gas gets to the market. So I would buy where YOU get the best results but that may not be consistent from area to area.

To reiterate, I have a Conoco and Citgo refinery in town so those branded stations get that gas. But the gasoline distribution system could not get gasoline cheaply to market if every drop of Citgo gas made in LA was delivered to Atlanta CITGO stations where there are no refineries. Or a better example is that the Shell station in town sells gas for the same price or cheaper than CITGO and Conoco. The nearest Shell refinery is hours away. The trucks get the 87 onboard the additive is added and away they go. This sounds bad but we would not even have $2.00/gal gas if it weren't for this type of distribution system.