lower octane gas in uzj 100?
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I Use Mid Grade (87 in CO) for daily use and Premium (91) for trips. No knocking. I know the manual for the 2005 recommends 87 or higher. not sure about the '99. This has also been covered in several other threads. Might be in the FAQ but I'm to lazy to look.
I use 87 without issue.
I mix betwen 87 and 89 around home....put in 91 and 93 for trips or when in mountains. The system is able to adjust easily with no harm or problems as long as you are not towing or using maximum performance of vehicle. Never had a knock from lower grade fuel...but do not run it continuously...more like a irregular rotation depending on prices, location, and expected habits upcoming week. 
I can't tell the difference... same everything just 10 bux more a tank. Others suggest the lower octane preignition is minimized by the engine auto adjusting the timing thus lowering horsepower. What you gain you lose. Seems to me, pick something and stick with it. I'm not a mechanic but I'm sure cronic preignition has negative long term consequences however our engine adapts and mine never ever pings.
Having worked in the fuel industry, it was suggested to us that a engine will make obvious ping noises under heavy load... indicating you need a higher rating. This is more common in newer high compression high performance engines. On the downside, higher octane gas may contain more water as it tends to sit around longer. I personally find vendor choice has more influence than octane rating. Different formulations work better in different engines. Ethanol content can be more of a minor issue with the lower grades.
Having worked in the fuel industry, it was suggested to us that a engine will make obvious ping noises under heavy load... indicating you need a higher rating. This is more common in newer high compression high performance engines. On the downside, higher octane gas may contain more water as it tends to sit around longer. I personally find vendor choice has more influence than octane rating. Different formulations work better in different engines. Ethanol content can be more of a minor issue with the lower grades.
Mid grade has been fine in my 04, I've never run low or high so I couldn't give you a comparison.
Several threads on this exact topic, search away.
It's also worth while to google octane and learn just exactly what octane means. Most people are surprised by what they learn.
I use 87 since I purchased it back in '03. Do not use 85.
Used 89 last time...put 93 in today....I had not given her the good stuff since early December so figured she deserved it.
We've been using the lowest octane fuel ever since we bought my wifes 98 LC in the early 2000's (maybe 2001??).
We live in Orange County, CA. It now has 237,000 miles. NEVER had a problem of any kind. Add high(est) octane when we go to Lake Tahoe for our winter vacations or going into altitudes but that's it.
Just bought our second (mine!) 98 LC this last New Years day! And will continue the same.
Mind you, we are like clockwork with our services.
We live in Orange County, CA. It now has 237,000 miles. NEVER had a problem of any kind. Add high(est) octane when we go to Lake Tahoe for our winter vacations or going into altitudes but that's it.
Just bought our second (mine!) 98 LC this last New Years day! And will continue the same.
Mind you, we are like clockwork with our services.
I run Shell V-Power 91 exclusively in my hundy ('00 w/ 136K). I've only had it for a couple of months so I'm really not sure what the PO ran through it, but I don't mind spending the money on good quality gasoline. I prefer Shell V-Power because of the nitrogen cleansers that they use, but any good quality gasoline (sunoco, conoco, chevron, etc) would be fine. Many have run lower octane without issue, but it says "premium gasoline only" on the gas door. That's enough for me. Besides, here in CO we only have 85, 87 and 91. I'd never run 85 (way too low of an octane IMO, even at altitude), so my thought process is, if I'm already paying for 87, buying 91 isn't going to kill me.
As for cheaper gas (Costco, Sam's club, Bob's Gas 'n Go, etc), I refuse to buy it. I bought some gas from a cheap fill station one time (I think it was giant eagle, but this was 10 years ago so I don't honestly remember), and there was more water in the gas than gas. Never again. Saving a couple bucks per tank just isn't worth it. I know that moisture can find its way into ANY brand of gas, but I've never had an issue with shell, so that's what I'll continue to use.
As for cheaper gas (Costco, Sam's club, Bob's Gas 'n Go, etc), I refuse to buy it. I bought some gas from a cheap fill station one time (I think it was giant eagle, but this was 10 years ago so I don't honestly remember), and there was more water in the gas than gas. Never again. Saving a couple bucks per tank just isn't worth it. I know that moisture can find its way into ANY brand of gas, but I've never had an issue with shell, so that's what I'll continue to use.
i've run 87 in my 99 for 10 years. Have +150K miles now with no problems whatsoever. Tried 93 in mine for a while several years back. No appriable difference in power or mileage so went back to 87.
I find that the ~$10 or so more a tank is easily offset by the ~1mpg better that I get. I run 93 V-Power in all my cars.
EDIT: If your going to run 87-ish. Dont fill it up with junk - go to a top tier distributor. Exxon, Mobil, Shell, Chevron, Turkey Hill etc
One more thing, the $10 difference a tank is nothing when it costs 60-70 to fill up. perhaps a cruiser is not your best bet now.
EDIT: If your going to run 87-ish. Dont fill it up with junk - go to a top tier distributor. Exxon, Mobil, Shell, Chevron, Turkey Hill etc
One more thing, the $10 difference a tank is nothing when it costs 60-70 to fill up. perhaps a cruiser is not your best bet now.
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I like the Shell gas too, but I believe you are mistaken on Costco gas. It is usually always the lowest priced premium grade around, due to the fact we are getting wholesale pricing. Plus, the best thing about Costco gas is the fuel is fresh. So much volume goes through the pumps at the stores, there's no time for fuel to sit in the storage tanks and collect condensation.
Also, I am trying to find the 60 mins story I recently watched on TV. They interviewed a guy at the refinery where the tank trucks filled up. He said all fuel from Exxon, Shell, Race track, etc... all filled their trucks from the same spout. There is virtually no difference in the gas makeup. The only thing that changes is someone like Shell will add a detergent pkg to the tank after fill up. The marketing behind Shell and the Exxons is unbelievably misleading to the public.
If I can find the story from 60 mins, I will post it up.
Holy crap, How Much more is Premium from Regular out there? In my part of Colorado it is exactly $0.20. Not sure about my math but even assuming a completely empty tank, $0.20 x 25.4gal = $5.08. Anyways I think the ovewhelming point is to pick Mid or Premium and stick with it. Use a busy, reputable gas station. Get a gas credit card. My Conoco card gives me 3% back on unlimited gas purchases. The $0.09 per gallon savings makes it the same or similar price as generics.
Your doing it backwards.
Higher octane fuel contains combustion inhibitors to prevent pre-ignition (pinging). Pre-ignition is less of a problem at higher altitudes (lower atmospheric pressure).
In reality I should switch to higher octane when we go down to the Bay area from Reno. However I never do and we haven't noticed any problems with pinging.
True if you're staying at altitude, but if you're pulling a load up to the vacation place then higher octane may be a good idea to help with the power/heat of the grade. Similarly, I probably wouldn't want 85 in my tank if I came back down to sea level.
What is the connection between vehicle load and fuel combustion rate?
Heat! Wider throttle positions = increased compression temps. Combine that with some hot spots (carbon deposits) and you set yourself up for pre-ignition knock. Most vehicles won't exhibit knock until under load and it typically gets worse as intake temps rise.