Ever since I purchased my kitty last October I've generally driven it with the transmission mode selector in the normal (Granny) setting unless I think I'm going to need the performance.

I play a mileage game with the trip computer set to always display average mileage. I leave the 'A' trip alone, accumulating average mileage over multiple tanks of fuel and always reset the 'B' trip at each fill-up. The point is to drive around town trying to keep the average mileage as high as possible. I've been averaging about 22mpg around town. I compare the 'A' trip mileage to the 'B' trip mileage as a health check to see if mileage has significantly changed.

My assumption has been that Granny mode would provide much better gas mileage. However I've been pretty tired of relatively sluggish Granny performance and have wondered about my mileage assumption. Last week at a fill-up I decided to try a tank with the transmission mode selector always in Sport and have been a bit surprised. I really can't tell if my mileage is any better or worse but I'm much happier with the kitty's pep.

I'd love to get your experiences and opinions on the merits of sport versus granny and any noticeable differences in gas mileage.

Thanks,
beg3yrs

 

I never put mine in regular mode, always in sport mode. It always shows average mileage at 18.6 mpg. Average speed is always right around 35 mph. I don't drive it very hard or very much.

I would suspect that you would not really see a significant difference between the two modes unless you drove much more aggressively in sport mode than you do in regular.

 

I agree with Kevin. Now if you were driving around town in manualy selected second or third gear most of the time, you would see a difference.

 

Looks like I'm going to try more tankfuls with the tranny in sport mode. Given both your inputs today and another 40 mile round trip to work with pretty much the same MPG as in granny mode, it's nice to have the throttle response when you want (I almost said 'need' but that really isn't true) it.

I suppose my assumption that ****-poor performance (granny mode) would equal better mpg but further thinking is that a better match between the motor's power curve and getting it onto the road (sport mode) is the better choice for MPG.

So, what was Jaguar's intention of having two transmission modes?

I'll guess that granny mode might soothe the fears of a more timid driver or passenger.

Other thoughts?

 

I was driving down the road today with the cruise control set at about 55 mph. I glanced down at the tachometer and noticed that it was hovering slightly over 2000 RPMs. I thought that was kinda weird. I glanced at the shifter and it was definitely in "D", then I noticed that the transmission was in sport mode. I pressed the little button, and instantly the tach dropped down to about 1500 RPMs. I'm certain that the higher RPMs at 55 mph would have a negative impact on the fuel economy. I'm guessing that the car shifts into 6th gear at a higher speed in sport mode. If so, if you're driving down the highway at 70 and the car is in 6th gear regardless of whether sport mode is selected or not, then the sport button won't have any impact when driving that steady speed. But if you're driving at a slower speed and the transmission chooses a lower gear because the sport button is selected, than that would have an impact on fuel economy.

 

Thanks for the note. I'll watch for that kind of behavior and report back.

I sure wish my older XK8 had a 6th gear!

 

I think sport mode may prevent the torque converter from locking, as well as keep it out of overdrive. Really not sure though.

I usually see ~24mpg for around town driving, only rarely putting it in sport mode. Highway driving will average ~28mpg, and on flat level roadway the instant mileage gauge will read ~31mpg @ 70mph.

 

6th gear, in sport mode, does come at 70 mph - approximately. Once you reach 70, you can always slow back down to 60-65 and it'll stay in 6th.

 

I do that too, but my game is to see how low I can get my mileage. When I'm being excessively lead footed, I can get about 13 city mostly short trip stop and go. I get about 24mpg on the highway.

 

LOL!!! Try driving with the parking brake on. The should drop it by a MPG or two. At least until the caliper and pads seize.

 

LOL at people with $80000 cars trying to save cents on the dollar vis a vis gas mileage

 

Well, he's got a '99 Jag, that he may have paid as little as $9,000 for, or less, depending upon mileage and condition.

 

Yep! $9,928 to be exact and it remains a great bargain (yes, I am of "Scoa tish" descent. I'd do it again too. These cars didn't hold their value but mostly they were well-maintained by the first owners who paid so dearly.

I figure all those pennies saved will add up to reduce the cost of the parts for the next repair or modification (like drop your top), whichever comes first.

BTW, I played with the tranny settings today and did not replicate the behavior of Rev Sam's XKR. Rereading the owner's manual it says for my model the two selections merely change the shift points. This seems to be the case. It would be interesting to know if the later model's manuals say anything different.

I'm beginning to believe that for 'normal' (not lead-foot) driving, you just might do better mileage-wise in sport mode as those shift points, while higher in RPM, might just keep the overall drivetrain at a more efficient point for transferring power to the road.

 

I don't think so. I may be completely wrong, but I think the engine uses less fuel when it turns more slowly. The ECU keeps the air/fuel ratio at the optimum point for best efficiency when you drive with a light foot on the pedal. If the engine is turning faster, it's going to suck through more air, and that will cause it to burn more fuel.

 

Let's just say that the difference in gas mileage would almost certainly be insignificant (my guess would be 1-2 mpg at most, and almost the same at least) in relation to the enhanced enjoyment that you will have while driving it in sport mode. (once again, assuming, of course that you basically drive at the same relative pace)

The six speed transmission probably does have different settings than the four speed. I could see where overdrive in the six speed would only come into play at 70 or so, as another poster said.

 

I just read that Chrysler is installing an EIGHT speed transmission in some of their new models, primarily to increase fuel economy. The new 300 with a 5 speed gets 27 mpg, while the same car/engine with the new 8 speed ZF transmission gets 30 mpg.

Here's the article: http://editorial.autos.msn.com/blogs...e-77fdd83a27ce

 

I see your point but I think this really has to do with efficiently getting up to the speed at which you want to drive. Lead-footing it certainly sacrifices fuel economy to get to speed quickly while going with a very light foot on the pedal takes forever to get so speed, leaving the motor and fuel system in an accelerating condition for a longer time. Probably a happy medium in there somewhere.

Anyway, I think I agree with another poster who said the insignificant difference in mileage between the two modes doesn't warrant losing the joy of the responsiveness you get when you let the kitty roar.

 

Going to more and more gears for better mileage seems to support that at different speeds there is an optimum gear that maximizes your fuel economy by matching the drive train's performance to the requested speed and acceleration. Taken to the limit, an infinitely variable transmission (and there are some out there) would be the absolute best.

 

I agree that more gears should help to get the best fuel economy at different speeds. My XK8 is not set up for best mileage at 75 mph. Probably is set up for 55 to 65 mph. Have to check the tach more closely next time, but I am usually just going with the flow of traffic.

 

I do most of my travelling on the highways. I get the best mileage at around 100-120km/h. I watch the "range" steadily increase early on then slowly decrease as I continue. Once I hit closer to 130, the tach starts rising and the range decreases much quicker.

When in sport mode, I get less economy around town but the difference isn't noticable on highways or two line highways (with overtaking).