What????? I presume the OP is in the USA, not the land of Oz. If that's the case, then 87 is the lowest octane the OP can find and 87 will be perfect for his XJ. 89, 91, etc. willl not damage/harm the OP's XJ in any way........again, anything higher than 87, in a properly tuned/maintained vehicle designed to run on 87, is just wasting money.

 

87 octane fits my wallet quite nice. The wife's Buick is supposed to have premium in it's supercharged V6 lawnmower engine.
My Chevy pickup seems to run better with mid grade, but maybe it's playing mind games with me.
My '74 Malibu sits in the hangar most of the time, so I use 100 low-lead avgas in it to avoid the ethanol problems.
My El Camino has a 507 inch Caddy in it @ 8.6 to 1, and will run fine on the cheap stuff.

 

Actually, RON+MON/2 is the formula for AKI. AKI is the US and Canadian standard. If you see "RON+MON/2 Method" on a US gas pump, that tells you that the octane rating is expressed in AKI.

I learned this on the forum for my other car where these Australians kept posting about using 98 octane fuel. It caused some confusion until someone pointed out that the Aussies had 98 RON gas, which corresponded to about 92 or 93 AKI gas in the US and Canada. RON usually runs about 6 points higher than AKI for the exact same fuel.

 

Mostly anecdotal but I have also heard that on older carbureted engines, the ethanol was hard on the carb seals and floats and regular unleaded contains up to 10% Ethanol (E10). Ditto for older lawnmowers and snowblowers. I typically run premium in carbureted engines as it isn't supposed to have any ethanol in it.


Just to add fuel to the fire, the DOE website has this statement:
"The energy content of ethanol is about 33% less than "pure" gasoline, although this varies depending on the amount of denaturant that is added to the ethanol. Thus, vehicle fuel economy may decrease by up to 3.3% when using E10."
http://www.eia.gov/tools/faqs/faq.cfm?id=27&t=10

 

I could go all day on how the E10 mandate is a crock. The freaks at EPA were wanting to eventually push E15 and E20. The only time ethanol is great is in an engine designed with the high compression to utilize its full energy potential.

 

...so I can run e20 in my aventador?

But seriously, is that ethanols big thing? High compression for it to be using more of its energy?

 

You may want to check that. I see you're in Canada, but in the US at least, in order to be considered "Top Tier" gas, it must contain 8% to 10% ethanol. That includes all octane levels. The gasoline at the majority of stations in the US contains 10% ethanol in all gasoline coming out of their pumps.

The Top Tier certification requires the ethanol because it is supposed to help clean injectors on fuel injected engines. When you find a station selling non-ethanol gas in the US, it may be perfectly good gas or even better gas than the fuel down the street at the Top Tier station, but it can't be considered Top Tier gas because it doesn't have ethanol.

The little boxer engine in my other car has 12.5:1 compression from the factory and requires at least 92 AKI fuel to avoid detonation. For complicated reasons I won't go into here, some people find it very desirable to run non-ethanol gas in that car. However, I find that in the rare instances I'm able to find non-ethanol fuel, the premium octane levels are not available. Usually non-ethanol fuel is sold at 87 or 89 AKI, the octane levels people usually use for their lawnmowers and fishing boats, which (not coincidentally) are usually carbureted.

I have a hunch that's the same in Canada, and the premium fuel you're pumping is still giving you ethanol at greater cost with no advantage. Down here, the pumps usually say something like "All fuels contain up to 10% ethanol by volume."

Ethanol is not added specifically for high compression engines. As I noted above, people who drive the same model as my other car actively seek out non-ethanol fuel for its high-compression engine. Those engines can run ethanol, but you have to jump up to E85 before the ethanol makes any difference in performance.

The published reasons for adding ethanol include emissions and top end cleaning of engines. The ethanol is supposed to burn cleaner. It's also supposed to help keep fuel injection systems clean. It's supposed to be a "renewable" fuel (since it's processed from corn or switchgrass), so its advocates think that using it will stretch out the oil supply. There is conflicting research on how beneficial ethanol actually is, since you also get a corresponding reduction in fuel economy, causing you to burn more fuel when you use it.

The real reasons we have ethanol in our gasoline have to do with the corn, nitrogen and chemical lobbies. During WWII, nitrogen production in the US reached its peak. It was used in bombs. After WWII, industry had the ability to produce all this nitrogen and nothing to use it for. Corn production requires a lot of nitrogen for fertilizer. So the nitrogen industry teamed with corn farmers to overproduce corn. All that corn required other chemicals for fertilizers and pesticides, so the chemical lobby had a real interest in it.

They overproduced. We had more corn than we could eat, so the corn producers started looking for other markets in which to sell it. They started putting it in cattle feed (which before WWII was primarily grass), leading to the huge amount of corn fed beef we eat now. They made a sugar substitute, high fructose corn syrup, and undercut the price of cane sugar wherever they could to get that stuff into our food supply.

And they STILL had corn left over. So they started using it to make ethanol. The corn/ethanol lobby was successful in convincing the US and other governments that ethanol was a miracle fuel that would save the world. They came up with all these reasons why ethanol was better than gasoline, which was made by evil oil companies controlled by A-rabs.

Our government (and others) went for it. If the chemical and corn producers had their way, we would all be driving E85 vehicles. Really the only reason we're not is that the oil and automotive lobbies are strong enough to resist the corn lobby. Who'd a thunk the oil lobby would be the voice of reason in all this?

So next time you're driving out through Missouri or Kansas with rows upon rows upon rows of corn flashing past you on both sides of the highway, THAT's why we have ethanol in our fuel. On average the costs and benefits cancel each other out, so that we're really no better or worse off than we were before.

 

Shell V-Power 91 is pure gas up here. Says on the pumps and you can call 'em up and ask. The mandate for E10 presently only extends to 87 octane. Other brands blend E10 throughout their entire product line. Marinas are a great place to get pure gas, too. Well... if you drive a boat, lol.


Additionally regarding the bull**** "ethanol is better for the environment" scam, while ethanol itself does indeed burn cleaner (set aside for a moment how some vehicles experience such a decrease in fuel economy that more gasoline is burnt...), corn is an incredibly inefficient plant to derive sugar from, and requires a lot of heat. It's commonly processed in coal-fired plants.

And yes you're right, commercial corn is far from a renewable or even remotely "green" plant. But that's a discussion for another site lol

 

I think the website is www.pure-gas.org that is a database of non-ethanol stations.

 

Your politicians are better than ours.

 

I'm very skeptical about that so called "no ethanol" list. Is there a special/secret refinery those stations get their "no ethanol" gas from?.....I doubt it.

 

LOL. The refineries are not secret. Stations can purchase non-ethanol gas from their fuel distributors. Usually only the off-brand or mom-and-pop stations buy it, because the big name brand stations want (or are contractually required) to sell Top Tier gas.

The Pure Gas site is legit, but when I was looking for E0 I found that it was often out of date or just plain wrong. The list is maintained by readers reporting what they find. If you find a station selling E0, you can go on there and add that station to the database. I could have updated the ones listed that I discovered were no longer selling it or were closed, but I just didn't really care enough to do that.

 

Ethanol isn't added at the refineries, it's added at the distribution layer, same place additives are poured in. All they're doing is making gasoline.

 

I have to say that I did get a little better mileage by switching to mid grade gasoline, but it was because of the only reason that it will increase mileage. I have the ignition timing set about 4 degrees advanced over stock and with regular I get some pinging, and the pre-ignition that causes pinging will lower your mileage(along with destroying the engine eventually).

With a carbureted 2.5L you need everything you can do to get more power

 

Anyone shed any light on the altitude vs lower octane thing? I read it has to do with atmospheric pressure and the compression ratios of engines and that relating to the octanes which are determined at sea level compression rates, they interact differently with the oxygen levels or some crap.