Return-Path: Sender: (Marvin Kaye) To: lml Date: Sat, 16 Aug 2003 14:21:29 -0400 Message-ID: X-Original-Return-Path: Received: from gw.nnsy.navy.mil ([199.208.213.35] verified) by logan.com (CommuniGate Pro SMTP 4.1.1) with ESMTP id 2530521 for lml@lancaironline.net; Sat, 16 Aug 2003 14:19:16 -0400 Received: (from uucp@localhost) by gw.nnsy.navy.mil (8.12.9/8.12.6) id h7GIJIqd022386 for ; Sat, 16 Aug 2003 14:19:18 -0400 (EDT) X-Original-Message-ID: <105650A3D206C84A9827EA79A55640FC019C647F@snnsvr222.nnsy.sy> From: Rumburg William J NNSY X-Original-To: "'Lancair Mailing List'" Subject: RE: [LML] Auto Gas in O-320s X-Original-Date: Sat, 16 Aug 2003 14:19:09 -0400 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain; charset="iso-8859-1" X-Loop-Check: X-Loop-Check-FW: I have been told that running 1/2 auto gas is good. Is this true? I tried using Mobil 93 octane for half of the tank and everything seems to run fine. Lorn- I've been burning 93 octane auto in my normally-aspirated 8.5:1 CR IO-320 for six years with good results. Octane isn't the problem. The real potential problem with gasoline is vapor pressure. Gasoline is formulated for Winter and Summer vapor pressures. Winter is the higher, to aid engine starting under cold conditions. The vapor pressure for Summer formula is very nearly as low as that of 100LL and I've never experienced a low fuel pressure problem in hot Summer or Fall weather. I have, however, gotten a low fuel pressure alarm (set for 14 psi on my injected engine) when running Winter formula on a hot Spring day. I'm certain that it was due to incipient vaporization on the low pressure (inlet) side of my engine-driven fuel pump. Fortunately, turning on the electric boost pump, which is located just ahead of the engine-driven pump, restored normal pressure. I had to leave it on for awhile. I've experienced this just a couple of times, after takeoff and at higher altitudes (taking a tank of warm gasoline to the lower pressure of high altitudes results in the same condition). When do refiners switch from Winter to Summer formula and when are their stations tanks clear of Winter formula? I don't know, but I've only experienced the problem during April and May. I noticed or think that I noticed that the fuel caps are harder to take off. It is almost as if the large rubber washers were expanding. Is this my imagination? The newer fuel cap washers (light pink color) are rated for gasoline, however, you should still remove and wipe them with silicon lube at least once a year for long life and smooth operation. How about some other comments and thoughts on using auto gasoline. Is it as safe as using aircraft fuel? It can't be too hazardous, about 1/3 of all small piston airplanes are now using it and the FAA issues STC s for it on certified aircraft. Bill Rumburg N403WR (Sonic bOOm)