i think older engines (200k plus) should use either midgrade or premium to reduce knocking

 

nope

 

Insightful post. Care to elaborate?

 

if you took two jeeps and from day one... one guy ran regular and the other ran premium... the insides of the engines after 200k miles would look like night and day...premium is cleaner fuel and wont dirty the oil up as much as regular does...its better for the engine in many ways...and if you think about it... its only a few bucks more to fill up...so in the long run. its worth it overall... it will keep injectors cleaner... valves cleaner oil cleaner.. and you will get a tad better milage...

 

I ran premium for one tank of gas and it ran terrible. It was hard to start on really hot days and just ran a little rougher at idle. Ran it all out and went back to the cheap stuff and my hard starts are gone. I dont have any ticks but a very slight tap. I do run some lucas fuel cleaner once a month but thats it for me. No science or math here for me, just some field testing.

 

i run premium at least once a month to clean stuff out and i havent had any problems ifanything i think my truck runs better on premium gas.

 

I think a lot of the ticking that is going away when switching to premium is more of a detonation tick going away more than anything. Most engines with higher mileage will have deposits in the combustion chambers, thus the combustion chambers are smaller (a little) and the compression is slightly raised. With the way most vehicles are programmed for fuel economy so they are on the lean side of things. The regular fuel just does not have enough octane in it to reduce the "pinging" that is occuring. And the premium has a higher octane rating which reduces or removes the "pinging noise". I used one tank of premium in my XJ when I first got it. And the noises went away. Since then I have run combustion chamber cleaner (like seafoam) through the throttle body. With using regular fuel it now runs like it did on premium before, no noises at all...

Just my theory though

 

i did a little homework back when my xj was my dd

i would run it because you figure if your on empty, to fill your tank to the top, or mine at least would take say 17 gallons in a 18 gallon tank at the gas station because it wont be literally empty,

so you take the current price in so cal for example which is 289 for regular at the station by my house, or 309 for premium x 17
everyone freaks out cuz it costs more but do the math=

2.89 x 17= $49.13

at 3.09 x 17 that is $52.53 to fill up. now idk about you but id rather take better care of my engine and spend the whole extra 3 bucks, whats 3 bucks anyways when your already spending 40-50? and if you say you cant afford the extra 3 then go buy a hybrid and let me have your xj for a parts car

then you factor in the increase in mileage, for me i was getting 13 mpg average on regular and 17 mpg on premium so lets take that 17 gallons and at 13 mpg your 49.13 is letting you drive 221 miles on 17 gallons, that means every 4.49 miles you drive costs you $1

now take that "expensive" premium you just put in your tank...
that 17 gallons will let you drive 289 miles, that will let you drive 5.5 miles per dollar.

oh wait you just went further on a gallon of premium and its better for your engine. better re think your regular octane strategy.
this is what i found now do what you wanna do but im sure an engine is an engine and youll get the same result as engines all function the same way

 

X2!!!

 

Sandaddict, Are you comparing ethanol to gasoline? If so, that's been beat to death on this thread. It's not higher octane giving you extra mpg because otherwise ethanol (89 oct) would give better mpg than reg gasoline (87 oct), and that's just not true.

 

5 pages, 70 posts, 1500 views and lots of opinions later, can anybody start backing up those opinions with facts. Unless I missed it, I can't find a link that says premium is all gas and no ethanol. Help me out here.

 

The pump has to say if it's got ethanol in it...at least in Iowa. I don't know how the rest of the world does it. Frankly, I don't care anymore. I'll put what I want in my Jeep and the mileage I get is indisputable, and I like that.

 

It's funny. All the anecdotal and empirical evidence (reduced knocking and improved MPG), and someone just quotes other websites as "evidence". What's your real experience in this subject?

I have seen a slight increase in power, and reduced knocking. I couldn't care less what some other website says. For me, the proof was in the results. Sure, it's gonna cost me a little more at each fill up. But I am good with that, considering the results.

 

Still waiting.

 

Stop waiting. Every State has different labeling laws.

http://www.fuel-testers.com/state_gu...anol_laws.html