Mk IX, 85 (UK) gals, plus 35,45,50,90 and 170 gals drop tanks. Late production models with 33 or 41 gal rear fuselge tanks plus 2x18 gal Mareng bags in wings. This gives a max of 162 gals internally (195 US gals) vs 221 UK gals for the P-51D with the 71 gal internal tank (or 73% of the Mustang's capacity).

I should add that this gave the Spit 67% of the range of Mustang on internal fuel. The less draggy Mustang had a 10% better range for the same power settings, basically because the Mustang cruised at a higher speed for the same power. The endurance for the same fuel was the same for both planes, but the Mustang's range was higher due to the higher speed. However that still changed the Spit from a short range fighter to an effective medium range fighter, because, as I've stated several times before, the fundemental limit on combat range is the fuel remaining for combat and return after drop tanks & (at least) some rear internal tank capacity is burnt off. But an effective combat radius of 400 (probably closer to 500) miles was well within the capacity of late model Spits, even if you require the entire rear tank to be burned off before combat. Simple calculation (note all based on UK gallons): Fuel left at start of combat (drop tanks gone and empty rear tank) 121 gals. Say 50 gals used in combat & escape (about 25 mins at max power) = 71 left. This equals 426 miles at 6 miles per gallon (medium fast cruise, not fastest cruise). Or 475 miles at most economical cruise (230 mph IAS). If less (say 20 gals less) is used for combat or (say) 20 gals are left in the rear tank at the beginning of combat this equals 546/609 miles on the same assumptions. Put a bigger rear tank in (say 75 gals) then the Spit becomes a good long range fighter, still not as good as the Mustang, but better than the P-47 and about equal to the late model P-38s. Interesting eh.

The rear tanks (there were 2) that were put in later run Mk IXs were 75 gallons, a bit bigger than the XVI's 66 gal tank because they didn't have the rear view fuselage.

To MF: We've been over the rear fuselage tanks. They were only used for ferry mission, not combat. They were much farther aft of the center of lift than the tank on the Mustang, and on a lighter a/c, had a much greater effect on center of gravity. The Mustang fuselage tank had to be at least half empty for combat, with the Spitfire it would have had to be almost totally empty, and converted to self-sealing which would reduce the capacity considerably. In any event, drop tanks aside, the increases in fuel capacity in the Spitfire, from MkI to Mk21 didn't quite keep up with the increased appitite of the more powerful Merlins, and later Griffin engines.

To AE My source gives range of the MkIA as 575 miles at economical cruising. Range for the MkXIVE (internal fuel) as 460 miles. Range for the MkVC as 470 miles. AS to the MkXVI, where did they put the extra fuel. It used the same wing as the MkIX, so no room there. If your talking about a rear fuselage tank, I covered that below. As to the MkXVIII, the argument was that the Spitfire was being developed for range comperable to a Mustang. The MkXVIII was a developement dead end. It's range increase was due to a new wing structure that was not developed further, or applied to later model a/c.

To MF: WAnt to go thru those numbers a little slower?? For the MkIX, regular internal tank ahead of the pit was about 95 gal., same as a MkV. In the MkVIII the redesigned wing allowed another 28 gal. In the MkXVIII that went up to 53 gal. with a 66 gal rear fuselage tank as standard (but still not usable for combat. So combat radius for a MkIX is on a fuel load of 95 gal. less what's burned in combat. For a MkVIII it's on 123 gal. less what's burned in combat. For a MkXVIII (with the more thirsty Griffin) it's on 148 gal. less what's used in combat.

To MF: First, how could it be 'not as good as the Mustang, ... about equal to the late model P-38s' when the late model P-38s had a greater combat radius than the Mustang?? Adding a larger rear fuselage that would increase ferry range, but not combat radius, for reasons given below. Note that the Mustang put the rear tank much closer to the CL, and was a heavier a/c, but the RAF still removed most of the rear fuselage tanks due to the effects on a/c handling of trying to fly combat with fuel back there. The Spitfire would have been much worse.

To MF If you want to talk about Spitfire developement, there was the Spiteful. Basically a strengthened Spitfire fuselage on a copy of the Mustang wing. But it's range on internal fule was still less than 600 miles, while range of the P47D at MAXIMUM cruise was over 650 miles, P51D over 900 miles and the P38L at economical cruise was nearly 1200 miles.

>>>To MF: We've been over the rear fuselage tanks. They were only used for ferry mission, not combat. They were much farther aft of the center of lift than the tank on the Mustang, and on a lighter a/c, had a much greater effect on center of gravity. The Mustang fuselage tank had to be at least half empty for combat, with the Spitfire it would have had to be almost totally empty,<<< The Spitfire IX manual has this to say on handling qualities with the rear fuselage tank: When the rear fuselage tanks are full there is a very marked reduction in longitudinal stability, the aircraft tightens in turns at all altitudes, and, in this condition is restricted to straight flying, and only gentle manoeuvres; accurate trimming is not possible and instrument flying should be avoided whenever possible. Aerobatics are not permitted when carrying any external stores (except the 30 gallon blister drop tank), nor when the rear fusealge tank contains more than 30 gallons of fuel, and are not reccomended when the rear tank contains any fuel. And this is what the RAF Mustang III manual says: When the fuselage tank is full, the aircraft is longitudinally unstable in all conditions of flight, and tends to tighten up in turns; until at least 40 imp gallons of fuel have been consumed from the tank, no manoeuvres other than very gentle turns should be attempted. (the rear tank contains 71 gallons when full) When carrying bombs or drop tanks, or fuel in the fuselage tank, areobatics are prohibited. So, in comparison, aerobatics in the Mustang were banned with any fuel in the tank, in the Spitfire with more than 30 gallons in the tank.

>>>For the MkIX, regular internal tank ahead of the pit was about 95 gal., same as a MkV. <<< Actually in most it was about 85 gallons. The larger lower tank was not fitted routinely until the Spitfire VIII, and late production IX/XVIs. >>>In the MkVIII the redesigned wing allowed another 28 gal. <<< The late production IXs and XVIs also had wing tanks, 2 x 18 gallons. >>>So combat radius for a MkIX is on a fuel load of 95 gal. less what's burned in combat.<<< Unless the wing tanks and/or rear tanks are fitted.