I believe the modifications to the GTS engine for oil consumption wasn't done
until 1994, so the 92 and 93 should be about the same.
That being said, I would like to point out that it appears to be much more of a difference between individuals than anything else. Some engines consume a *lot*, while others don't consume anything at all.
They did get the "average" down in 1994 though.
I think that in a way the S4 and GTS are rather different cars. The GTS is
more quiet, which is nice. And the looks do differ a bit.
But at the other side, we're not talking about big differences, to be honest. And I think that engine wise, the S4 is a safer car.
So once more the question becomes: is the GTS worth the extra money?
For me the GTS is worth more than an S4, but I like original stuff, and in good condition. And my next car would be one with redwood, leather, automatic, preferably no sunroof, and preferably with memory on both seats. And in a nice color. That will be difficult.
Oh, and it should be a '92 or '93, with the original rims, so that I have the RDK intact.
Tricky indeed. :)
I have a late model GTS - 25th from last - and it definitely consumes more oil than my previous 88 S4 or 91 GT did, but its not excessive. I change oil every 5-6000 miles and use probably 2-3 quarts between changes so I would say about 1 quart every 1500-2000 miles. I rarely had to top-off the oil the earlier 32V engines. I can't say whether the piston drain holes are drilled-through or not, but I did read somewhere that Porsche designed the GTS engine for oil consumption to increase engine life. I'm okay with that.
95 auto, polar silver
My experience with the '93 GTS (an early model - no.5 in '93) is that it
consumed a quart about every 1000 miles. However (disclaimer time), I did not
drive the car at very high speeds or rev it up "too often". Relatively "mild"
For further reference, the following is a excerpt from an email the "new" owner of my '93 GTS sent me....
I was hoping you could shed some light on the cars oil consumption. I know these cars were designed to use oil at the expense of engine wear. PCA web says up to 1 liter per 600 miles!
On the trip from Atlanta to Dallas I checked before leaving and had a line ¾ the way between the high and low mark. About 650 miles outside of Atlanta a got a low oil warning. Luckily I had a quart with me.
I just had the timing belt and oil changed and set the second tripometer to zero. Only about 450 miles into my road trip this weekend I checked the oil and I was again down almost 2/3rds from the high mark.
I am definitely on track for 1 liter per 600 miles. My mechanic thought it should be somewhere around 1 liter per 1500 miles.
Bert Silvestre [firstname.lastname@example.org]
I just bought a ’93 GTS several months ago. Unfortunately for me I seem to have gotten one that likes the oil maybe more than others. I am seeing about a quart every 600 to 700 miles. Now I must admit since the car is new for me I have been VERY aggressive with accelerations and speed…160+ which I am told only exacerbates the consumption. I passed all emissions fine here in the great state of Texas with the car just passing the 76k mark. Hope this helps!
My GTS is a '93 US model, with a build date in early '92. I have nearly 130,000 miles on it and out of habit, check the oil frequently. I add one quart about every 5,000 miles and my go pedal frequently sees the floor. I seem to go through tires faster than I go through oil. I've used Mobil 1 15W50, Castrol Syntec 5W50, and Pennzoil synthetic oils.
Most people I've heard from who have the GTS have much worse consumption that this, however.
A friend has a 93 US GTS and the consumption is pretty bad. It is about a quart in every five hundred miles. From what I understand the fix was not applied until 94. It involves removing the pistons and drilling a drain hole.
Other than consumption there do not appear to be any other problems like clogged cats and failed smog inspections. Although another 93 I looked at was having emission problems in the 100K mile range. The owner had on the advice of his mechanic had added a water injection system. I am not sure the water injection accomplished little more than draining the washer tank.
All of the 928s I have seen that do not leak oil - good luck finding one - seem to use no oil between changes.
Now only if I could find this blasted oil leak, I might be able to finally sell this car.
Dan the Pod Guy
I bought a '94 GTS in January (62K miles). Drove it 4K+ miles in June/July to the 928 OCIC in Denver. Most of this was routine driving, with speeds in the 70-80 mph range, but it did have a little bit of spirited driving in the Rocky mountains. I added 1 qt of oil late in the trip (using Mobil 1 15W50). It does have a small leak, so that may have impacted some of the "usage".
I've had essentially NO oil consumption on my current and previous S4's during highway driving (50K-110K miles on them). When I've driven them on
the track, however, they do consume about 1 qt per 150 miles!!
West Chester, PA USA
Sent: Sunday, February 04, 2001 7:51 AM
Subject:  Re: Considering a 928s4 (LONG) - long again
Dave S. wrote:
> Nope. '84-'86 "Euro" (16V) had 97.0 mm bore x 78.9 stroke, '85-'91 100.0 x
> 78.9, and the GTS's '92/'92-'95 100.0 x 85.9 Some GTS's apparently had oil
> consumption problems as pointed out below by Walt.
All Euro "S" 16-valve engines from _mid/late '80_ through to the
introduction of the 32-valve engines had a 97mm bore. All other
dimensions/specifications above are correct.
My understanding of the "oil consumption problem" on the GTS engines relates to the introduction of forged pistons on these engines. This
was the first time the Porsche V8 used forged pistons. All previous Porsche V8's had used cast pistons. Because of different expansion characteristics between the two piston types, "cold" piston-to-bore clearances are not the same. Due to the different grain structure
and increased grain density of forged aluminum vs. cast aluminum, the forged pistons "grow" slightly more than cast ones when both have
achieved operating temperature. What this means is that the engine with forged pistons will require a slightly larger piston-to-bore clearance when cold. This makes it a little harder for the piston rings to seal, hence increasing the possibility of oil consumption. High compression engines using forged pistons (like the GTS) are often more critical of proper operation during the break-in period when new.
I was unaware of any "porous block" condition, but my standard disclaimer applies.... I don't know everything about anything, and some of what I think I know is not necessarily correct. ;^)
From: Marc Thomas [email@example.com]
Sent: Wednesday, February 27, 2002 10:54 PM
Subject:  FW: GTS Oil Consumption - repost from 12/11/99
From: "Marc Thomas"
Date: Sat, 11 Dec 1999 10:03:12 -0800
Subject: GTS Oil Consumption
I have talked to many GTS owners and Porsche about the oil consumption of GTS'. The fact of the matter is that the oil consumption is usually in specification, and the technical reasons for the consumption are valid.
The GTS pistons have unique oil scrapping system (combination of ring tension, type of ring and drain back capacity) designed to leave more than the usual amount of oil on the wall during each stroke, this is to improve piston to wall lubrication, so more oil ends up in the combustion chamber to be burnt. There is also a change in the material of the piston. Keep in mind that it is the first forged piston used in a 928! There are also specifications on cylinder to piston clearances, which fall within a specified tolerance, and may be responsible for variances in oil consumption within models. Since I have measured many GTS pistons, I have found that the tolerances do vary slightly even within any one group.
The design of the piston is very different than S4 or earlier pistons, both in design and material. Why they made this design change is simple, Porsche wanted to improve the durability of the GTS under extreme driving conditions. It is the same reason that they added a oil cooling
system to the manual transmissions! Constant improvement! But it did have a "down side". In my view, a quart of oil is a lot less expensive than an engine rebuild? Of course, I can revise your pistons and eliminate the oil consumption..... but it cost more than a quart of oil!
I have seen GTS with 2000 mile per quarts, and I have seen them with 450 miles per quart. Porsche made a decision on a design and the jury is still out.
So, If the oil consumption is out of the spec, then there is generally another reason why...breathers, guides, etc. Always check the plugs as
indicators of internal engine condition...also use compression and leak down testing.
Drive hard and drive safe, and have fun! (and keep a quart of oil in the
Marc M. Thomas
From: Jim Bailey [firstname.lastname@example.org]
Sent: Tuesday, March 20, 2001 4:31 PM
Subject:  Re: oil consumption on a GTS
The pistons for the GTS are shorter so they do not hit the counter weights on the crankshaft when they are all the way down . In the redesign they moved the rings on the piston . When you increase the stroke (how far up and down the piston moves) the cylinder head limits how far up it can go . Additionally side loading on the piston increases as the piston gets closer to the crankshaft the connecting rods work at a greater angle which is detrimental to oil control and wear . The longer movement of the piston and the larger diameter circle that the big end of the connecting rod and crankshaft scribes the closer it comes to the oil pan which increase the amount of oil being beaten into a froth . So the added windage and leaking of some compression past the rings causes more oil vapors / fumes to be drawn into the intake and burned . The 2.72 ring and pinion ratio for the GTS increased the RPM at normal driving speeds further increasing oil burning and engine wear form a 2.2 ratio to a 2.72 . At cruise speed the engine turns 23 % faster burning more fuel , oil and wearing out the engine faster .