Karl F. Rau wrote:
> I (my brother) needs some information about the various octane
> booster products on the market, He owns a '68 MGC which has a
> compression ratio of 9.0:1...the manual calls for 98 octane...
> obviously not normal pump gas
Your brother's 1968 MGC should run without pinging on current
93 octane pump gas. (Is he having a problem with pinging? Or,
is this a question based on the manual specifying 98 octane?)
So, the obvious question is, if the manual says 98 octane, why
do I think the car will run on the current 93 octane gas? I
speculate that, as with most cars in the 60s, the octane
specification uses the "Research" (RON) method of octane
rating. (The other currently used method is the "Motor" (MON)
method.) The ratings on pump gas is the average of the
"Research" and the "Motor" methods. (You will see the
formula (R+M)/2 on the octane labels at the pump.)
The Research and Motor octane rating methods tend to differ
by about 10 points. Thus, most 93 octane pump gas will
have a Research octane rating of 98, and a Motor octane
rating of 88. (Some variation occurs.) Thus, with the
MGC manual calling for a 98 octane (Research), 93 octane
gas (which is likely to have a research octane of 98) should
work just fine.
To lend some more credence to this, the owner's manual
for my 1970 TR6 (8.5:1 compression) specifies the use
of 100 octane fuel (Research Method). It runs just
fine on 93 octane (R+M)/2 gas, and will give only slight
pinging under severe load with 92 octane gasoline. (I
found this en route to the VTR National, where I found
that all the gas stations where I needed to get gasoline
only had 92 octane in their "premium" gas...)
For a more detailed explanation see Bruce Hamilton's
excellent FAQ on Gasoline. (See the VTR WWW pages
for the link from http://www.vtr.org/maintain). He
also has a fair bit to say about additives for
boosting octane.
--ken
VTR WWW Maintainer -- http://www.vtr.org
'70 & '74 TR6 Daily Drivers
--
Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 |
PO Box 868 | Voice: (603) 885-9604
Nashua, NH 03061 | Fax: (603) 885-0631
|