> Do we notice a increase in fuel economy when we use higher octance fuel?
> A power increase? Any increase? well besides cost obviously.
> I use 92 octane 76 fuel consistently, for me it makes a difference, the
engine makes more power, smoother too.

i've been keeping close records on my 88 bus since i bought it new. six
brands of gasoline and three octanes. as far as i can tell, there ain't a
nickel's worth of difference in the brands or the octanes. that is, 87
octane gets just as good mpg as 92/93. only when you calculate the
miles/dollar do you see the difference! and the higher octanes get lower
mpd. :(
if you like, i can send you the raw data or the processed "report" (dippy
little thing written in REXX).

but that's MY bus with MY driving style(s) in MY region, using the gasolines
blended and sold hereabouts. other regions and other gasolines may (and
probably will) vary. and you can't count on Shell gasoline actually being
"Shell" ... i've seen Exxon and Amoco and Texaco trucks filling up the Shell
stations around here ... which is probably why the gasoline brand doesn't
seem to matter. :(

joel
oh, what the heck .... here's the brand comparison. :)

brand     octane  tanks gallons    cost        miles       mpg  $/gal
miles/$
Amoco    R87     46    592.0     654.38   12,077.3  20.4  1.11  18.46
Amoco    R89     23    300.2     343.26     5,774.0  19.2  1.14  16.82
Amoco    P92     23    305.8     395.49     6,111.8  20.0  1.29  15.45
                          92  1,198.0  1,393.13  23,963.1  20.0  1.16  17.20

Bp       R87        46    574.5     627.48   11,577.0  20.2  1.09  18.45
Bp       R89        23    313.6     367.39    6,231.3   19.9  1.17  16.96
Bp       P92        25    308.9     397.89    6,139.3   19.9  1.29  15.43
                         94  1,197.0  1,392.76  23,947.6   20.0  1.16  17.19

Chevron  R87     45    604.6     668.75   11,984.0  19.8  1.11  17.92
Chevron  R89     23    295.6     355.33    6,042.9  20.4   1.20  17.01
Chevron  P92     24    304.1     399.03    6,175.9  20.3   1.31  15.48
                          92 1,204.3  1,423.11  24,202.8  20.1   1.18  17.01

Exxon    R87      46    617.5     679.13   12,270.3  19.9  1.10  18.07
Exxon    R89      23    297.8     345.06    5,655.4   19.0  1.16  16.39
Exxon    P92      24    302.3     389.09    6,205.6   20.5  1.29  15.95
                         93  1,217.6  1,413.28  24,131.3   19.8  1.16  17.07

Shell    R87       45    581.6     644.01   11,317.3  19.5   1.11  17.57
Shell    R89       23    301.6     353.11    5,997.0   19.9   1.17  16.98
Shell    P92       24    311.9     392.46    6,338.1   20.3   1.26  16.15
                        92 1,195.1   1,389.58  23,652.4  19.8   1.16  17.02

Unocal   R87     43    580.1     618.57  11,418.2  19.7  1.07  18.46
Unocal   R89     21    269.1     311.73    5,332.1  19.8  1.16  17.10
Unocal   P92     21    274.1     349.98    5,581.4  20.4  1.28  15.95
                        85  1,123.3  1,280.28  22,331.7  19.9  1.14  17.44

Z-other  R87      2     27.0      28.62      533.6  19.8  1.06  18.64
Z-other  P92      1       3.5        4.28        55.6  15.9  1.22  12.99
                         3     30.5       32.90      589.2  19.3  1.08
17.91

Z-start  R87      1     15.7      14.10        0.0   0.0  0.90   0.00
                         1     15.7      14.10        0.0   0.0  0.90   0.00

                           7,181.5  8,339.14  142,818.1