Super or Regular Unleaded?

ReaperSRX

ReaperSRX

Member
Joined
May 26, 2003
Messages
589
Age
52
Location
New Liskeard, Ontario
I have different people locally telling me defferent opinions on what kind of fuel i should be using in my 2000 SRX 700, what your take on this debate?
 

It depends what your doing with it. If your talking about normal trail riding then yes you want to run super unleaded or 91-92 octane. If your talking about drag racing then that is different. On a stock motor for short runs regular 87 octane will give you better results. The 92 gives you more of a "cushion" for trail riding. It allows for more tempature swings, wide open lake blasts, and more forgiving to moisture. The 87 has more BTU's per gal and will provide more power (on a stock motor), quicker throttle responce, and faster accleration. hope that clears things up. ===SRXSRULE===
 
Yeah I figured someone was going to ask that. The reason being is that the 92 is overkill for what it actually needs. 89-90 would work fine most of the time but the extra octane is the cushion for the long lakes runs which heat soaks the motor and can start to cause hot spots in the cylinder (the same reason they run the ECS plugs). Now, if you got some moisture in the fuel, the extra ocatne is going to help keep is from detonating as easy as it would of if you were running 89-90 and got the same amount of moisture. Does that answer your question? ===SRXSRULE===
 
Not really! lol I read your message a few times and it didn't make a lot of sense to me. This is how I understood it... 91/92 will buffer moisture laiden gas from detonation problems??? When will moisture detonate? Seems to me, that wouldn't be a problem. My understanding with the higher octane gas in srx's and higher compression engines, is that detonation occurs at a lower temperature, so the engine doesn't need the extra heat. I think that came out right.lol I do agree that 91/92 is over kill. I work for an oil refinery in a high octane producing unit, and can tell you (at least here in MN) that nine times out of 10, you are getting higher than 89 octane at the pump when it says 89 octane because I work at the largest refinery in the state and we have a problem with the crude we run, and the volumes we run that we give octane away. That will change soon due to a new hydrocracker being built, but for the next year or so, the consumer is gettiing a deal (lol), expecially at the 87 octane level.
 
I run What ever the pump has for premium 93 octane my sled is full throttle when ever it can be.Lake runs are the best anyways why did yami put the minimum octane sticker on there it will run with them all?
 
Chance..... I will just stop trying to explain it. I do have a question for you though. I'm an auto tech in central Iowa and yesterday we towed in 3 cars that had just fueled up with gas. 1 of them made it 3 blocks home, 1 a 1/2 mile and the other one never made it away from the pump. Now....here is why. The station was pumping about 40% WATER! How does that even happen? They just had there tanks filled on saturday and these guys got gas on sunday night. I still have the 96 k-1500 on my hoist this morning and it needs about 600.00 in injectors replaced now. ===SRXSRULE===
 
Wow! that is alot of water. Well, the only thing I can think of is to look at the variables that can change between the refinery and the stations. Each tank at our refinery, and I'm sure at all refineries goes through product specs by the company and customers. I'm not saying every tank of product, but each gallon of gas is blended to achieve the min. octane rating for that gas. Each is sampled before they are pumped to the loading rack. So if the samples are lost/errored, this is a possibility. Another is maybe the tank they used to load the tanker was near empty and pumped the tanker full of the condensate build up that happens often if the refinery doesn't pump the tank down enough. Another of course is maybe the shipper them selves had cleaned/repaired the tanker that delivered the gas to the station, and after deconing the truck, never totally drained the contents, thus "watering down" the load. Another thing I thought of is, what shape are the stations tanks in? If they were low when the tanker filled them, and they previously were leaking rain/groundwater into the tank, then the adding of new fuel will dispers all that water around the tank, instead of just on top. Well I have had enough typing, not sure if anyone will even read all this crap. Rules, if you make it to the end of this, try re-explaining your deal with the octane gas for me please, I'm really interested.dd
 
chance-
Here's my take on the octane thing. When looking for high performance (racing) you want to run the lowest octane possible without getting detination. For trail riding, you want the extra 'cushion' (higher octane) Rules was talking about incase there are impurities in the fuel. This will help prevent detination that can take out your engine. Consider it added protection like jetting a little fat instead on the the very edge incase of a temp change.

As for what to run in your SRX, use what is suggested in the manual. You can run lower, but you're just taking risks when you don't need to.

monker
 
Chance....that is correct. As you know....octane slows the burn process in the cylinder. Detenation happens when the pressure or temps in the cylinders is too high for the fuel to maintain its controlled burn front and it explodes in the cylinder (KNOCK). What actually happens is the burn front starts too early in the compression stroke and instead of completing the burn at the top or near TDC the flame races across the cylinder, bounces off the wall and meets back up in the center , or close to, of the piston and then explodes when the pressure overcomes the remaing fuel charge in the cylinder. Thats why when you get that nice dime sizes hole in the piston from detonation. Now....you guys want to cover preignition?? and make this really confusing? LOL ===SRXSRULE===
 
Some places actually do dilute their gas with water to increase their profits.I used to live next door to a guy that delivered gas and diesel to farmers.It wasnt a Marathon station these people got bad gas from was it?
 
Yikes!

As far as I know, water in your gas doesn't cause detonation, super heated water would become steam, and that doesn't burn either...

The octane argument is a long standing one. Most guys buy a new motorized toy and think they will pamper it with the best gas they can buy, and they 'feel' a difference.

While it's hard to take two sleds that are both stock, run cheap gas in one and premium in the other and test them scientificly, you can see results when racing your buddies or when refueling.

A stock motor with no mods is usually made to run 87 and should, by upping the octane you can lose a few hp. But, by upping the octane and advancing the ignition timing, you can gain some hp! On a sled, it's just not practicle to be messing with the timing all the time on the trail, so in general, it's a waste.

On a car with a distributor though, you can see gains as soon as you bump the timing up. I just did this on my VW. It's got 10:1 compression and is EFI, runs on premium anyway. I didn't use a timing gun or anything, just advanced until I got a teensy bit of spark knock. Or preignition. This is the edge of controllable combustion, go too far and you'll hurt parts, too little and you're a dork, keep trying!hehe

The theory behind advancing the timing in the first place, is that the motor will then use all of the available fuel to make power. Start the spark earlier, and you've got more time to build pressure and heat against the piston surface. It works well. I suggest experimenting with something with a distributor, not your wifes daily driver, hehe. I know you were thinking it!
 
What would you run in a stock Viper then. It requires 89 but I have been running the highest that I could find on the trail. I figured it would help to stop detonation. I am wrong in running 91 or whatever I find?
 
I have never heard of water content in the fuel causing detonation. I remember a few years back they marketed water injection to help prevent detonation. The water would likely cause a misfire, or incomplete burn of the fuel?

Detonation - occurs when heat and pressure in the combustion chamber cause the fuel to preignite. This causes multiple flame fronts in the combustion chamber instead of a single flame kernel. When the multiple flame fronts collide and you get a sudden/severe rise in cylinder pressure.

Preignition - occurs when a spot in the combustion chamber becomes so hot that it acts as a source of ignition before the spark plug fires. This preignition tries to push the piston in the wrong direction and can create enough heat to burn a hole in the piston. (preignition may contribute to or cause detonation).

Higher octane fuel - higher resistance to preignition....detonation.

Use whatever fuel your engine requires. Don't forget that there is a difference between "pump octane" and "research octane". If I'm not mistaken a pump octane of 88 is about the same as a reseach octane of 93.
 
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