Gas Consumption SLK230 top up/down results

**SLKCop** · 07-09-2008

Ok, as promised in an earlier thread, here's the final results of my 'research' regarding gas consumption while driving with top up and top down.

In order to keep things as consistent as possible I use the same gas station [QuikTrip, 93 octane] for both tanks of the test. I also ensured the tire pressure was the same for both tanks [30 front / 33 rear]. I didn't run the tank all the way empty on either test, but I tried to refill as close as possible, so for the top up test I drove 301 miles and for the top down I drove 259 miles. I don't have any modifications to the engine/air intake/etc. It's all stock.

On both tanks, I drove maximum of 70 mph, using cruise control as much as possible to maintain the same speed.

With the top closed up I used 11.371 gallons for 301.0 miles. That equates to 26.471 miles per gallon.

With the top down I used 9.677 gallons for 259.0 miles, which equates to 26.764 miles per gallon. Slightly better!

The week I drove with the top down was slightly cooler than the week with the top up, so I don't know how much that affects gas mileage, but all in all it appears as though I get almost exactly the same gas mileage regardless of whether the top is up or down.

**KTownAMG** · 07-09-2008

Interesting comparison, I'll have to try that with mine. I'm actually glad to see the price of oil has actually gone down the last couple of days, we'll see how long that lasts... BTW, I can't remember if I told you or not, my wife and I will be SATX the week of 18 August, any chance you'll be around?

Tummy · 07-09-2008

That's interesting. On my previous car, an Audi TT roadster, we got around 25% better MPG with the top up. I haven't done a formal test on my current car, but I think it does better with the top up. We're going on a 2000 mile roadtrip in August and I'll try it then.

livefreeordie · 07-09-2008

26 seems low, i have the same year/model and get around 30 hiwy.

**SLKCop** · 07-11-2008

Quote:

Originally Posted by livefreeordie

26 seems low, i have the same year/model and get around 30 hiwy.

Yeah, when I'm doing only highway driving, I get 29-30 mpg. This was a mixture of highway and city driving, mostly highway, though.

**SLKCop** · 07-11-2008

Quote:

Originally Posted by KTownAMG

Interesting comparison, I'll have to try that with mine. I'm actually glad to see the price of oil has actually gone down the last couple of days, we'll see how long that lasts... BTW, I can't remember if I told you or not, my wife and I will be SATX the week of 18 August, any chance you'll be around?

How long will you be there? I won't be off work until that Wednesday & Thursday. Maybe we could meet halfway, depending on your schedule? I think Kevin [DesignoSLK] is also going to be in the area around the same time if I remember correctly.

**DesignoSLK** · 07-15-2008

Quote:

Originally Posted by SLKCop

How long will you be there? I won't be off work until that Wednesday & Thursday. Maybe we could meet halfway, depending on your schedule? I think Kevin [DesignoSLK] is also going to be in the area around the same time if I remember correctly.

That depends largely on KTownAMG, in an indirect way. I'll give you a call and explain.

Steve, just so you know, work sucked this weekend.

cousjcc · 07-15-2008

I'll be around the 18th of Aug for sure, as I live in SA

.

For the top up/top down mpg comparison, I think the top down decreasing mpg really only comes into play at highway speeds over 65mph so if you did any city driving at all, even if it was just 20% of the total miles driven, it could skew your numbers down to make top up/top down appear more even. At any rate, the SLK has a relatively low profile and small footprint, especially the kompressor version, so top down driving would only alter wind resistance slightly. The mpg should be pretty darn close, within 1-2mpg tops I would say, even for 100% highway driving. Wind screen could come into play as well (having vs not having one that is).

The only way to get a "truely" accurate comparison would be to pick the same 150-200 mile stretch of highway, going the same direction, approximately the same temp/heat index (affects road temp therefore tire "stickyness"/traction which *could* in theory affect mpg), with the same amount of wind within a mph or 2 coming from the same direction. Real world tests are very difficult to make very "scientifically accurate". Personally, I'll just take your results and run with them as my reason to drive with the top down!

matejo · 07-29-2008

How is consumption related to speed? Any relation to torque too? I know that it's not the only rule "you drive slower - you use less gas". I think we'r getting close to science and SLK's now

Tummy · 07-29-2008

Wind resistance increases approximately with the cube of the speed, so for the same distance the energy required is approximately proportional to the square of the speed.

The engine is the most fuel efficient at the torque peak.

07-09-2008	#1 (permalink)
SLKCop Click it or Ticket! Join Date: Mar 2008 Location: Burleson, Texas Vehicle: Black/Black 2002 SLK-230 Kompressor [6MT] Other Toys: 2007 Toyota Tundra Posts: 363 Country: Thanks: 81 Thanked 101 Times in 56 Posts	Gas Consumption SLK230 top up/down results Ok, as promised in an earlier thread, here's the final results of my 'research' regarding gas consumption while driving with top up and top down. In order to keep things as consistent as possible I use the same gas station [QuikTrip, 93 octane] for both tanks of the test. I also ensured the tire pressure was the same for both tanks [30 front / 33 rear]. I didn't run the tank all the way empty on either test, but I tried to refill as close as possible, so for the top up test I drove 301 miles and for the top down I drove 259 miles. I don't have any modifications to the engine/air intake/etc. It's all stock. On both tanks, I drove maximum of 70 mph, using cruise control as much as possible to maintain the same speed. With the top closed up I used 11.371 gallons for 301.0 miles. That equates to 26.471 miles per gallon. With the top down I used 9.677 gallons for 259.0 miles, which equates to 26.764 miles per gallon. Slightly better! The week I drove with the top down was slightly cooler than the week with the top up, so I don't know how much that affects gas mileage, but all in all it appears as though I get almost exactly the same gas mileage regardless of whether the top is up or down. __________________ Mike 2002 Black SLK-230 To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Ike and the results of Gustav	UK-C200	Off Topic	2	09-13-2008 12:33 AM
my slk230 can not open the top	nycboy55	Help and Support	3	01-21-2008 03:25 PM
SLK350 dyno results	Ynot	General Modifications R171	2	01-11-2007 08:48 AM
Dragstrip Results	FishtailnZ	SLK R171 General Discussion	15	08-25-2006 10:18 AM
Dyno results thread	easty	Performance MODS for the R171	7	08-20-2006 02:06 PM

07-09-2008	#2 (permalink)
KTownAMG Senior SLK World Member Join Date: Jan 2008 Location: Germany Vehicle: 09 SLK AMG 55 Posts: 183 Country: Thanks: 14 Thanked 36 Times in 15 Posts	Interesting comparison, I'll have to try that with mine. I'm actually glad to see the price of oil has actually gone down the last couple of days, we'll see how long that lasts... BTW, I can't remember if I told you or not, my wife and I will be SATX the week of 18 August, any chance you'll be around?

07-09-2008	#3 (permalink)
Tummy Elite SLK World Member Join Date: Dec 2006 Location: EWR / CLE Vehicle: 2005 SLK350, 2004 Infiniti FX45 Posts: 283 Country: Thanks: 1 Thanked 42 Times in 24 Posts	That's interesting. On my previous car, an Audi TT roadster, we got around 25% better MPG with the top up. I haven't done a formal test on my current car, but I think it does better with the top up. We're going on a 2000 mile roadtrip in August and I'll try it then.

07-09-2008	#4 (permalink)
livefreeordie Senior SLK World Member Join Date: Oct 2007 Location: Rochester,NH Vehicle: 2002 slk230K 2008 Honda CRV Posts: 153 Country: Thanks: 0 Thanked 9 Times in 9 Posts	26 seems low, i have the same year/model and get around 30 hiwy.

07-15-2008	#8 (permalink)
cousjcc Senior SLK World Member Join Date: Jun 2008 Location: San Antonio, TX Vehicle: '09 SLK 350, Capri Blue/Black interior, Premium, Heating, AMG hood fins, window tint (a must in TX) Other Toys: Sold my motorcycle /cry Posts: 162 Country: Thanks: 10 Thanked 39 Times in 20 Posts	I'll be around the 18th of Aug for sure, as I live in SA . For the top up/top down mpg comparison, I think the top down decreasing mpg really only comes into play at highway speeds over 65mph so if you did any city driving at all, even if it was just 20% of the total miles driven, it could skew your numbers down to make top up/top down appear more even. At any rate, the SLK has a relatively low profile and small footprint, especially the kompressor version, so top down driving would only alter wind resistance slightly. The mpg should be pretty darn close, within 1-2mpg tops I would say, even for 100% highway driving. Wind screen could come into play as well (having vs not having one that is). The only way to get a "truely" accurate comparison would be to pick the same 150-200 mile stretch of highway, going the same direction, approximately the same temp/heat index (affects road temp therefore tire "stickyness"/traction which could in theory affect mpg), with the same amount of wind within a mph or 2 coming from the same direction. Real world tests are very difficult to make very "scientifically accurate". Personally, I'll just take your results and run with them as my reason to drive with the top down!

07-29-2008	#9 (permalink)
matejo SLK World Junior Member Join Date: Jul 2008 Location: Slovenia, Europe Vehicle: SLK 200, 2000 (R170) Posts: 8 Country: Thanks: 0 Thanked 0 Times in 0 Posts	How is consumption related to speed? Any relation to torque too? I know that it's not the only rule "you drive slower - you use less gas". I think we'r getting close to science and SLK's now

07-29-2008	#10 (permalink)
Tummy Elite SLK World Member Join Date: Dec 2006 Location: EWR / CLE Vehicle: 2005 SLK350, 2004 Infiniti FX45 Posts: 283 Country: Thanks: 1 Thanked 42 Times in 24 Posts	Wind resistance increases approximately with the cube of the speed, so for the same distance the energy required is approximately proportional to the square of the speed. The engine is the most fuel efficient at the torque peak.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)