I would think that the V6 would get slightly better mileage. They are both fairly close though. Speaking strictly for myself, I picked the V6 because it is more highly developed and based on the reports I read, pretty reliable. The 4.2 V8 appears to have most of the bugs of the 4.0 V8 worked out and should be fairly reliable also but maybe not as the V6. The V6s are easier to find as they make up about 75% or so of the S-Types made.

Happy Hunting:

Mike

 

I've had 2 of the Jag V6s (a 2.5 and a 3.0) in X-Types, and, now have an 06 S - Type with the 4.2. The S- Type I have gets better fuel economy than either of the X -Types I previously owned. I typically get about 28 - 30 MPG on interstate trips, and, 18 - 20 in town driving. The first couple of long trips I took in the S-Type , I was impressed by the fuel economy it got. I've put about 5K miles on the S since I bought it ( with 48K on it) with no problems. I never had any problems with either of the 2 Jag V6s as well.

Regards:
Oldengineer
06 S-Type VDP
08 Saturn Aura XE 3.5

 

On solo highway trips back and forth to Florida to visit her parents, my wife averages more than 33 mpg in our 2005 S-Type 3.0. I don't think the 4.2 could match this....

Bought it in mid-December with 18,000 miles on the odometer. She's now closing in on 32,000 miles....

 

Do not underestimate the sturdy V-6 3.0. Two years ago in late June, We visited my son who lives in Ft. Mojave AZ. (adjacent to Bull Head City). We live in Upland, CA (30 miles east of LA) My wife had a 3.0 X-Type and it didn't miss a beat the entire trip. It was a tad on the warm side and we had the a/c on 72* the entire trip. We started out with the temps at 90+ and in Needles the air temp indicator read 110*. It was 117* when we pulled into his driveway..
We averaged about 28 mpg for the 500+ mile trip and I had the cruise set on 75 for the Victorville to Needles run..

 

Jon89 - what speed does she tend to do? I'd expect a 4.2 to get that mpg fairly easily as I get that in my STR, if I behave.

 

Jay:

Since I bought the S-Type, I've made several trips from my house to Pittsburgh on I-79 which is pretty hilly. With my cruise set on 75 for the WV portion of the trip, she's been consistently giving me 30 MPG. Made the same trip a number of times in the 3.0 X-Type I used to own - the best she ever did was 28, typically she averaged about 26.

Regards:
Oldengineer

 

I have a 2003 S-type with the 3.0 L. On a trip from Sanford, FL (north of Orlando) to Sarasota, with 80-85 mph cruising speeds (with lots of 95 mph bursts), I was able to achieve 28 mpg. My top speed for the trip was 107 mph and I never drove below 65 mph on the highway portion of the trip. The road is mostly flat with few changes in alignment and grade.

During regular driving, I get around 22 mpg in mostly suburban/city driving and 24 mpg on mostly freeway commutes.

I am very satisfied with the vehicle and love the way it eats up highway miles. The S-type is the finest road car built in my opinion.

I have had experience with an XJ8 and found city mileage to be approx 2 mpg below what I am getting with the S-type.

As far as reliability goes, I don't have much experience with the 4.2, however, I would think that, since the transmission is the same, that the V8 would strain it more if you drove the car hard. I imagine that the V6 could do a limited amount of damage.

 

The transmission changed with the years: started as the Ford 5-speed one and later the ZF 6-speed. The ZF can handle more than even the STR can put out so should not suffer from "strain" or damage.

On the flat my STR easily gets 34mpg between about 45-80mph when cruising.

My long-term average is 23.7mpg, which shows the impact of junctions etc. (And of an occasionally heavy right foot!)

 

jagV8,

On the Florida trips, she typically runs between 72 and 74 mph on all five of the interstates that she drives, using cruise control, with the A/C (or heat) set to maintain a temperature of about 70 degrees in the cabin.

 

Thanks.

Looks like the V6 & V8 do indeed do about the same mpg.