Unless it is a top tier fuel,such as Shell.Then all of their grades have the good amount of detergents in the fuel. So the best advice for regular unleaded people,is use a top tier fuel.

 

I'm on my second RX with 129K on this one. Nothing but 87 octane except for some tests with premium. No difference in economy or power. Never had a valid CEL and I changed the plugs at 125K and they looked like new. For the last about 80K I have been using an off brand, called Delta in NJ, without any problems. Problems with less detergent in regular and off brands was fixed over 10 years ago but the rumors still exist.

 

You may be right,but this is what I discovered re;top tier fuel.

 

Riggins fuel!! i got my best millage coming back from the shore last year on that stuff.

 

Since I have gotten back to the U.S., I have experimented with a number of fuels. Sometimes correcting assertions I made earlier. The two gasolines I have tied for #1 are Sunoco Supreme Unleaded and Chevron Supreme Unleaded. I seem to get the best mileage on them and the lowest number of CELs running these two. I have also seemed to have a good, but not as good as the top two, running Mobil (even though I don't like running Mobil1 for my oil anymore)

Top name brands that I have had issues with on mileage and CELs (especially A/F sensor codes, not just P0171 errors): BP, Shell.

I plan to give Shell another shot next time I fill up (though I suspect nitrogen is a sheer marketing ploy on Shell's part). My girlfriend has had a CEL virtually everytime she has filled up with BP with her Expedition, though sometimes the cel (an A/F sensor) is pending as I check it when the vehicle is back after having filled up.

However, I'll gladly take issues as such over the garbage I had in Mexico. See my comment in post 10 of this thread made when I was still in Mexico.

 

"(even though I don't like running Mobil1 for my oil anymore)" Lex,have you ever tried the Mobil-1 0W-40?

 

Yes, that was the best of the bunch in my opinion, but my consumption issues didn't stop until I used additives

 

So what about midgrade, wouldn't that be a combo of regular and premium?

 

That's exactly what it is, here in Cal. anyway. When you buy 89 (mid grade here) it mixes half from each grade (87&91) as it's being pumped in mixer valve in the pump.

 

I think thats how all the stations do it.What I would be curious to know is,is the 89 octane enough to keep the timing advanced for performance? Seems mine still has the most power on the 92-93.(I have tried all three grades) but if gas goes up to $4.00 a gallon again,I`m going back to regular.The real strange thing about using regular gas is,in the summer it actually runs pretty good on it.(once it figures out where to adjust itself) but as soon as that winter blend crap comes out,forget it! Runs like garbage then.(should be the other way around,cool air in winter vs.warm air in summer)

 

I have noticed at sea level here in Miami, my RX hated 87 the few times I ran it as a test. The power loss was quite noticeable. For 89 octane you might not notice a loss at higher elevations (even running 87) and depending on your driving style. Yes, warmer air can also negatively affect performance.

I might have tired lower octane in Mexico at the 7000+ altitude I was at, but for the few times I tried it (and knew from others experience) what foul garbage it was compared to premium (which was basically the lesser of two evils for many years until they started to make some progress in improving the premium).

 

Yeah,I Guess the winter blend fuel is just not good fuel.

 

The problem with gas today is that it's a commodity. It's bought and sold at various stages of the refining process. My understanding is that most of the major oil companies and all of the smaller ones sell oil/gas between each other. So by buying "Shell", "BP", "Chevron", etc, you don't really know whose gas you're getting (and I'm not sure it really matters).

 

sktn77a- I visit several forums on a daily basis so I don't remember which one the post was on.... but, a guy who supposedly drives a tanker that delivers to numerous brands of stations said that the fill operator presses the buttons to add the proper amount of whatever additive (s) that particular brand station uses (and proper amounts) as the tanker is being filled. I believe him, that's the reason different brands of gas may indeed be quite different when they came from the same tank farm. Often, many different brands of tankers are seen leaving the same tank farm on deliveries. We have a tank farm about 1 1/2 mi. away from us (not refinery, just filling station for the tankers) and the big white trucks (all alike) carry several different major brand decals (all on each tanker), though it's a Chevron farm and carries that decal on the truck cab. I have a friend who spent his career in managing the pipelines in the western states for the oil companies (engineer, I'm not sure whether chemical or something else). Under a major area like ours (So Cal.) there are lots of huge pipelines under this area (and all the way east to Phoenix) that carry the refined gas to the farms for distribution. There is no name on that gas when it is in that pipeline, hence the reason it is often the same fuel UNTIL it's pumped into the trucks for delivery. You wouldn't find gas from someone like BP that uses ethenol mixed with some brand that didn't, but maybe that's even added at the tank farm, I don't know.

 

I used to run regular in my rx300 when i first got her. Then for some reason i went to premium (91) for quite a while. I didn't really notice any better performance, but i did notice a tank lasted longer.

Then one day i tried to go back to regular and the car made knocking noises. So i've been back on premium.

I figure it will get me better mileage and save my fuel filter and sensors.