The exchanges on unleaded gas (petrol to me) are fascinating but it occurs
to me that it may not be that simple in regard to especially US mil veh of
WWII. The logistics and supply of US forces was enormous, including all
manner of home comforts such was the scale of the operation. It would
appear unneccessary to have foraged for fuel and even so continental
Europe, the UK and I believe German forces used leaded - unleaded was
unheard of.
It may be that WWII gas engines were leaded as the norm, true multi-fuels
came later and I am still trying to define the exact requirement for the
Rolls-Royce B series even with the manual to hand which helpfully states
"Petrol of 70 octane rating for B40, 60, 80, 81(Mk 5, 6, 50 & 60)" ; these
are the 6.4:1 CR engines and 80 octane for the B81 Mk 7, 8, 70 & 80 - the
7.25:1 CR straight 8. However for use below -5F the American spec is
MIL-O-3056 Amdt. 1 Type C. Perhaps someone can turn up this spec and see
if its a leaded fuel.
It seems there are many UK vehicles in the US with the B series unit eg.,
Ferret, Humber Pig, Saladin family, so it might be nice to know for sure.
Once the holiday season is over here I shall try to dig up someone in RR
themselves for a definitive answer - don't hold your breath!
As a matter of interest it was Mr Pratt and Mr Witney (Dependable Engines)
that first started adding tetraethyl lead. In one of the first radial
engines, developed on govt. money, there was a design fault that caused
both valve failure and low power output vs poor consumption owing to
necessarily rich running, the lead additive was the cure-all. We followed
suit when the Merlin was found to be a trifle short of grunt vs the FW 190,
in this instance the lead content was raised to allow more supercharge/revs
with no detonation viz., open the throttle more! The lead content then
used, and maybe still is, in AVGAS 120 octane was some 20 - 50 times that
in pump fuel!
The whole issue is comprehensively covered in "The Power to Fly" by L.J.K.
Setright which my library is trying to re-locate for me; and I reccommend
it as a must read for those of a mechanical interest, covering all military
piston aero engines starting with the Liberty. Should the memory be proved
faulty I'll correct myself when they finally track it down! (Or get the
reference copy from the Royal Aircraft Establishment - Farnborough!!!!)
All the best for '97
Richard
Southampton UK