From a Northern Irelander:

"Suckin Diesel" should only be used to describe a situation which has recently improved.

The situation should have been so bad that little or no progress had been made for some time. It should only be said after an event or action which allows further progress to be made.
John: What are you doing Dave?
Dave: Trying to get my computer to work.
John: Been at it long?
Dave: yeah about 3 hours mate, I can't seem to get it switched on. Any ideas?
John: Have you tried plugging it in and flicking the switch on the wall??

(Dave plugs PC in and flicks switch. PC starts to boot up.)

Dave: "Ahhh...now we're Suckin Diesel!!"
by Flarkey August 26, 2004
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A state of one's selfbeing. Or an expression of good progression.
Very good, doing well.

(Thank u 2 Colin + Edith 4 improvin th english language!)
How's it goin?
- I'm suckin diesel!
---or---
How's that project comin along?
- It's suckin diesel!
by Sam Baynes July 17, 2004
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Using this phrase is a way of informing someone you listen to the mindless ramblings of colin and edith on BBC Radio 1. Bring back Mark and Lard... pleeease!!
I'd rather spend the afternoon suckin diesel than listen to colin and edith.
by matt-leics July 20, 2004
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1 Having a great day, generally feeling good about ones self.

2 To fellate the star of pitch black

See www.suckin-diesel.net
1 Q How you doing?
A oh im suckin diesel!

2 Giving head to vin diesel
by Craig Perry July 28, 2004
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Word of Irish origin meaning to be doing well.
"Hey, how are you today"

"Ah i'm suckin-diesel mate"
by Mike Bastin July 15, 2004
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Irish slang for being drunk or intoxicated.
AWWW bejaisus look at the state of Mickey tonight, hes suckin Diesel
by Lee_full March 9, 2005
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