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Old 05-21-2022, 05:03 PM
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I'll try 89 octane mid-grade, first

Originally Posted by Effduration View Post
I have been running several M54 engines (E53, E39, E46) with regular 87 octane since 2003 with no issues.
Good idea, but the last vehicles I tried that on didn't like it:
  • 1) '66 Chevelle with a 327 c.i./400 hp 11.25:1 compression engine, 800 cfm carbureted, no engine computer, used for racing and also some daily driving, and
  • 2) '69 Chevy C-10 358 c.i./375 hp 10.5:1 compression engine, 750 cfm carbed, used for towing and daily chores, as well, also without engine computer to watchout for knocking.

Neither engine liked 87 octane, and the 327 would get 100+ octane gas for racing, and ran OK just piddling around on slow street useage at 89 octane, but preferred premium (with additives). I switched to 427's (the first with 12:1 comp., the second with 14.25:1 compression), and went full-on racing with it after 5 years/ 5000 miles. Meanwhile, after I put the 358 engine in the truck, it showed that the daily commute of 120+ miles required 89 octane, and I mixed that with premium on hot-weather long tows to races (towing the Chevelle' trailer).

But, the X5 does have sensors to detect problems, and can take out timing to suppress them, so it'd probably work for me, on my 3.0i X5, even being of reasonably high compression. It's worth a try.
01 BMW X5 E53,3.0i-5L40E, 7/13/01
topas-blau,Leder-grau,"resto-project car"

14 Lexus ES350,3.5L-U660E
09 HHR Panel,2.2L-4T45E
04 Chevy 2500HD,6.0L-4L80E
98 GMC Sierra 1500,5.7L-4L60E

66 Chevelle Malibu 2dr ht.,327>441c.i.-TH350>PGlide/transbrake
08 Cobalt Coupe,2.2L-4T45E
69 & 75 C10s,350c.i.-TH350
86 S10,2.8L-700R4
73 Volvo 142,2.0L-MT4
72 & 73 VW SuperBeetles,1.6l-MT4
64 VW,1.2l-MT4
67 Dodge Monaco 500 2dr ht.,383c.i.-A727
56 Chevy 210 4dr,265c.i.-PGlide
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