fuel consumption gas vs diesel - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 01-29-2003
Member
 
Join Date: Nov 2002
Posts: 89
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
jklewissf is on a distinguished road
fuel consumption gas vs diesel

A couple of weeks ago there was a message string going about gas versus diesel engines and I was challenged when I made the comment that you get more hours of operation out of a gallon of diesel.

I just stumbled across the following on a web site called boatsafe.com.

How much do gasoline and diesel engines consume?

Diesel engines consume about 1 gallon per hour for every 18 hp used. You can estimate the number of gallons consumed per hour by multiplying horsepower used by 0.055.

Note: An engine at cruising speed usually uses only about two-thirds of its maximum available horsepower. Most marine engines are designed to run continuously at between 60 and 75 percent of maximum speed. Diesels tend to be more toward the top of the range.

Gasoline four stroke inboard engines need about 1 gallon per hour for every 10 hp used. The number of gallons consumed per hour can be estimated by multiplying horsepower used by 0.100. (see note above)
Reply With Quote Share with Facebook
  #2  
Old 09-09-2009
roline's Avatar
Cal 9.2 SilverSwan
 
Join Date: Jul 2000
Location: East Tennessee
Posts: 272
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 15
roline is on a distinguished road
fuel consumption

I've always used 18 HP per hr per gallon for diesel and 14.5 for unleaded gas. This assumes internal combustion engines, 4 stroke, normally aspirated. I did some research on small engine fuel consumption and it goes like this:
Diesel17-20 hp-hr/gal

Natural gas9-11 hp-hr/ccf

LP (propane)9-11 hp-hr/gal

Gasoline10-14 hp-hr/gal

The size of the engine, operating temperature, RPM, and Load all have an effect on the efficiency of energy conversion.
__________________
Cal 9.2 #19 SilverSwan

Last edited by roline; 09-09-2009 at 08:11 PM. Reason: add graph and more info
Reply With Quote Share with Facebook
  #3  
Old 09-09-2009
wwilson's Avatar
Chesapeake Sailor
 
Join Date: Jul 2000
Location: Herrington Harbor, MD
Posts: 579
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 15
wwilson is on a distinguished road
Quote:
Originally Posted by jklewissf View Post
Diesel engines consume about 1 gallon per hour for every 18 hp used. You can estimate the number of gallons consumed per hour by multiplying horsepower used by 0.055.
I am not surprised that diesel has a higher power density than gasoline, but have empirical reason to question the formula.

I have no reason to think there is anything at all special about my 55-Hp diesel that pushes 10-tons of fiberglass and lead around. It has routinely averaged 1 gallon per hour running at 2400 RPM of its design WOT of 3000 RPM.

Do I misread the formula?

respectfully,
Wayne
Reply With Quote Share with Facebook
  #4  
Old 09-09-2009
JohnRPollard's Avatar
Moderator
 
Join Date: Mar 2007
Location: Chesapeake
Posts: 5,680
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 10
JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough
An old thread, but what the heck...

Over the course of 8 seasons, our current 3 cylinder 27hp diesel has consistently burned about 1/3 gph during normal sailboat operations. We push it hard (2700-3000 rpm whenever we're motoring, except when docking and during warm-up/cool down).

Our previous 2 cylinder 18hp diesel burned about 1/4 gph during normal sailboat operations.

So the figures cited in the initial post do not sync with our real world experience. I know my brother's gasoline A4 has a burn rate about 2-3 times our engine. It's putting out a bit more hp (30, I think), but it's pushing a smaller boat too.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Pacific Seacraft Crealock 31 #62

NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT
Reply With Quote Share with Facebook
  #5  
Old 09-09-2009
Maine Sail's Avatar
Senior Member
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 5,264
Thanks: 9
Thanked 111 Times in 81 Posts
Rep Power: 15
Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice
Why not..

Old thread but why not.. My 44hp Westerbeke consistently burns .72-.74 GPH at cruise speed which is 80% of WOT and I measure it at every fill up. My old A4 used to burn well over a gallon per hour pushing a boat 9,000 pounds lighter..

I can't imagine anyone questioning diesels ability to sip fuel in comparison to gas engines guzzling it.
__________________
______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




© Images In Posts Property of Compass Marine Inc.


Reply With Quote Share with Facebook
  #6  
Old 09-09-2009
tommays's Avatar
Senior Member
 
Join Date: Sep 2008
Posts: 4,227
Thanks: 1
Thanked 24 Times in 24 Posts
Rep Power: 6
tommays will become famous soon enough
The Beta 2 cylinder gets 14 MPG pushing the C&C 35 at 6 knots

The 4 Hp almost NEW 2 cycle that pushes my J24 6 knots is not even close
__________________
1970 Cal 29 Sea Fever

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #7  
Old 09-09-2009
roline's Avatar
Cal 9.2 SilverSwan
 
Join Date: Jul 2000
Location: East Tennessee
Posts: 272
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 15
roline is on a distinguished road
I found an efficiency graph to add to the subject.
Attached Thumbnails
fuel consumption gas vs diesel-fuel-efficiency.gif  
__________________
Cal 9.2 #19 SilverSwan
Reply With Quote Share with Facebook
  #8  
Old 09-11-2009
clueless
 
Join Date: Aug 2009
Location: Houston/Austin
Posts: 184
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 5
dieselboy is on a distinguished road
There should be 4 lines for a Diesel.

PC or Non direst injected Diesel Engines.. PC stands for a pre cup injected
Di or direct injected
NA or naturally aspirated Diesel Engines
and finally..
DI / turbo..

The most efficient and powerful is the Direct injected/turbocharged engine
you can also add a sub line for inter-cooled..

trying to calculate the range of a Diesel with out this information is use less.
A Pc is the least effective at turning heat in to usable power.
the DI/T-I is the best at varying load and the most efficient at fuel-hours of operation. Its in the 90% range while a pc is more like 50%.
So when i see the term Diesel engine i just cringe..

Sorry, i will get off my sop box now and go back to my little corner of the world.
Reply With Quote Share with Facebook
  #9  
Old 09-11-2009
Stillraining's Avatar
Handsome devil
 
Join Date: Jan 2008
Location: LaConner,Washington
Posts: 3,477
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 9
Stillraining is a jewel in the rough Stillraining is a jewel in the rough Stillraining is a jewel in the rough
According to the calculations then..my 64 hp Perkins should be burning 3.56 gph...It is not as far as I can tell ...but I will have to have more opportunity to check it out over time to be sure ..so far I have only ran it about 2 hours...I cant ignore this feeling in my gut telling me it will come in closer to under 1/2 of that..I will be quite surprised if it does not...as using various other engine consumptions ratios I have around here to compare it with says that calculation is all wet.
__________________
"Go Simple...Go Large"

Relationships are everything to me..everything else in life are just tools to enhance them.


The purchase price of a boat is just the admittance fee to the dance...you still have to spend money on the girl...so court one with something going for her with pleasing and desirable character traits others desire as well... or you could find yourself in a disillusioned relationship contemplating an expensive divorce.
Reply With Quote Share with Facebook
  #10  
Old 09-11-2009
christyleigh's Avatar
Senior Member
 
Join Date: Dec 2001
Location: North Brookfield, Mass.
Posts: 935
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
christyleigh is on a distinguished road
Quote:
Originally Posted by dieselboy View Post
the DI/T-I is the best at varying load and the most efficient at fuel-hours of operation. Its in the 90% range
Gee... you just made me feel good about my 75hp yanmar
__________________
Stan
'Christy Leigh'
NC 331
Wickford/Narragansett Bay RI
Reply With Quote Share with Facebook
Reply


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

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Diesel fuel RSchneider Gear & Maintenance 4 10-19-2009 09:39 AM
Diesel fuel filters ahoyjim General Discussion (sailing related) 0 01-06-2006 06:47 PM
Fuel Return Ratio pma_foyl Gear & Maintenance 8 07-22-2004 01:22 AM
is diesel fuel compatible with lined tank? johnbonner31 Gear & Maintenance 1 12-27-2002 02:10 AM
old diesel fuel capedoryus Gear & Maintenance 1 12-17-2002 07:14 AM


All times are GMT -4. The time now is 05:19 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012