octane rating in the XJ 4.0 V8
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03-31-2008, 09:43 AM
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03-31-2008, 12:00 PM
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03-31-2008, 12:16 PM
RE: octane rating in the XJ 4.0 V8
I have the 4.0 V8 in my '98 VDP, and have used "regular" 87 octane every third or fourth tank. Only noticed somewhat sluggish performance once. I think the quality of gasoline varies quite a bit, so that you can get really good lower octane, and really awful higher.
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04-01-2008, 11:02 AM
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RE: octane rating in the XJ 4.0 V8
When I asked a local Jag tech about fuel, he told me to stick with premium unleaded and use only Shell or Chevron. Those brands have additives that keep deposits from building up in your fuel system and on your valves. I had been buying gas wherever I got the cheapest price (the term "cheap" is relative when it comes to fuel) and I have noticed an improvement in performance and a slight increase in fuel economy since making the switch. When you think about it, an extra five cents per gallon is only about a dollar per tankful - not a lot if it prevents problems. My Mini Cooper also uses premium unleaded and I am doing the same thing with it, with the same results.
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04-01-2008, 12:07 PM
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RE: octane rating in the XJ 4.0 V8
ORIGINAL: skanoski
ilovetrains -- where do you live man! I thought 92 was pretty common, at least in the states. BPs here in Indiana tend to have 93.
ilovetrains -- where do you live man! I thought 92 was pretty common, at least in the states. BPs here in Indiana tend to have 93.
1600 miles on 91 so far no worries. 91 is about it for most places. I was looking hard today and did not see anything higher.
#13
04-02-2008, 11:04 AM
RE: octane rating in the XJ 4.0 V8
I live in central Missouri and there is 93 here and there at some places, just depends. The little local station I get all my fuel from mostly, has 91 on the pump, but the fuel is actually 93. He showed me the bill from the terminal. The fuel, by law, has to be at least what it says on the pump. Some of you might be thinking your buying 91 octane and its really 93. Depends on the station. Im too scared to try anything lower than 91. The manual says 91 or above, no exceptions. I figure the cost of engine damage would overrun any money saved at the pump, LOL
Blaze
Blaze
#14
03-25-2010, 12:49 AM
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Is this apples to apples?
OK...everyone is throwing about octane numbers. But which octane numbers? RON? AKI? RON + Motor divided by 2? Europeans use a different standard than we do, do lets all be sure we are talking about the correct octane rating. The only one of my Jags that I ever HAD to use premium (RON + Mtr/2) 91 was my supercharged XK8. My XJ8 VDP runs quite nicely on medium grade 89. Every once in a while I treat her a bottle of 108 octane boost and Techron. I think we should be more concerned about carbon deposits than octane, since I believe their is a knock sensor that retards the timing in cases of low octane knock. Watch out for the dreaded yellow reduced power indicator though, you could set it off. Anthony
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03-25-2010, 09:41 AM
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