Octane rating

[rjdelp7]

it was cheaper for them to build n/a engines, especially with the mistrust of turbo, which is evidenced right here in this thread some 30+ years later.

American manufacturing especially then was married to the tool/die/casts they owned at the time. they tacked boost onto existing platforms instead of building with boost in the planning from the beginning. however, it worked in most cases- though it never would cross into the black profit wise... they couldn't produce a boosted engine, which was intended for performance purposes every time back then, and make a decent margin. it's all about the money- and boost was a lost leader in costs.

there were some really mean aftermarket companies that outfitted those rigs, though. Callaway ran with a twin turbo+supercharged vette. Saleen produced several turbo and twin turbo cars. they made their money on those, but the profit was firmly in the black for them, and above what the OE could make... Face it- America wasn't making performance cars then outside of very specific lineups... and even those were mostly dogs.

as far as technology and metallurgical advancement- the sequential turbo's on my 6.4 are just plain badass. i've seen the exhaust gas temperatures running in excess of 1600* (nearing 1700*) for brief moments, and i've held over 1400* for several minutes straight. on average, i'd guess the EGT's temperatures sustain around 650* with momentary blasts up to 1k*. and those things work as good now as they did new, with 131K miles on the rig. i NEVER kill the engine (stopping oil flow through the turbo housings) when the EGT is above 300*- allowing cooler oil to circulate which saves bearings and seals. Coking (o2'less burn/same chemical reaction) happens when oil is beyond it's flash point (most oil's are in the 300~350* flash point range, high quality syn's are around 400) and it leaves behind a carbon film i've heard called 'cajun crust'... that stuff is impossible to remove from surfaces once it's formed... so, keep the oil flowing until things cool down- it only gets hotter after the keyoff. this little thing should happen with all boosted applications (diesel or not, turbo/s/c or not) : simply let the engine cool down before keyoff- especially if it's been ran hard.

as far as carbon build up, it is real and it's the fault of emissions controls. the CCV (on a diesel) or the PCV (on a gasser) spit bypass gasses which are laden with oil mist straight at the turbo vanes. bad juju. it DOES build up on them, and it CAN create an imbalance on the blades- and that imbalance can easily cause seal issues as the RPM's of the turbo increase, which breaks/wrecks seals and causes all kinds of issues. solution: reroute the vent (#1), and #2: use a high quality synthetic oil to protect the turbo bearings as well as disallowing coking on the blades from the misted bypass gasses.

ownership and proper maintenance of a boosted engine (especially turbo) requires more effort than a n/a engine. if that can't be done, then likely it's best you stick with n/a.

Leaving the engine idling, so it can "cool down". More waste of gas...AND TIME. Synthetic Oil, more expense. Exhaust temp 1700 degrees... No thank You, Mr. Ford

 

[ExpeditionAndy]

I've been absent here for years but just upgraded my '07 to a new '17 Expedition XLT. Any benefit to running 89 octane over 87? I'll no doubt run 93 when towing but it's a 75¢ bump here in Ohio. I run it in my S2000 but premium is required in that 'lil car.

I picked a '17 rather than wait for the '18s to cut any learning curve.

-- Chuck

Hi Chuck! Congrats on your new purchase - drive it in good health. Around town I run 87, if we are going on a trip like to PA, relatively level terrain I'll run 89 and when we hit the mountains in PA, then I fill up with premium. It seems to like the premium going up those long grades, I had power to spare.

 

[chuck s]

Better fuel economy with 87 rather than 89. I've less than 100 miles on the 3.5 Ecoboost so I don't have any real opinions either way. Picked it up Monday. New truck is smoother and quieter than the old but that's to be expected. The truck is really a computer on wheels.

This is my first turbocharged car since my XR4Ti blew up nearly 30 years ago. I'm assuming technology has improved since then.

Trips across PA are fairly routine for us. My daughter went to Gettysburg College and is now in Richmond and the quick way from Cleveland remains the turnpikes. Will see how the camper tows in a couple of months.

-- Chuck

 

[ExpeditionAndy]

Better fuel economy with 87 rather than 89. I've less than 100 miles on the 3.5 Ecoboost so I don't have any real opinions either way. Picked it up Monday. New truck is smoother and quieter than the old but that's to be expected. The truck is really a computer on wheels.

This is my first turbocharged car since my XR4Ti blew up nearly 30 years ago. I'm assuming technology has improved since then.

Trips across PA are fairly routine for us. My daughter went to Gettysburg College and is now in Richmond and the quick way from Cleveland remains the turnpikes. Will see how the camper tows in a couple of months.

-- Chuck

I grew up in Mechanicsburg, and my wife grew up in Enola, so we go back and for to PA a couple of times each year. Last year we made 5 trips in the old 05. Towards the end I was getting 14.5 MPG so I am really happy with the 17. Comfort level is pretty much the same but it is much quieter.