What is your opinion on [name_m]Diesel[/name_m]? I was actually talking about a different name and then brought up [name_m]Diesel[/name_m] and my husband really likes it! My husband and his dad both have “D” first initials and my husband is an engineer for diesel engines, so it does have meaning and isn’t just a random name. Also thoughts on the name as a sibling to our children? The other names I have really been loving lately are [name_m]Dieter[/name_m] and [name_m]Dietrich[/name_m], opinions on those are welcome as well. [name_f]TIA[/name_f]! 
Not a big fan of [name_m]Diesel[/name_m] myself. Are you sure your husband going to stay in the same job forever? [name_m]Diesel[/name_m] may have significance now, but in five, ten or fifteen years your husband may be doing something else. [name_m]Just[/name_m] things to consider! I know a few dogs named [name_m]Diesel[/name_m] but no human children. Also, google says [name_m]Diesel[/name_m] is a code name for Heroin on the [name_f]East[/name_f] Coast of the US…
PS- I think [name_m]Dietrich[/name_m] would make a lovely addition to your children!!!
Thanks @katiem333! Good thoughts on [name_m]Diesel[/name_m] as well. I also know of a dog with the name. Didn’t know about the code name, not a great association! As far as my husband’s job, nothing is for sure, but he will stay in his job as long as he is able.
I just think of trucks and [name_m]Vin[/name_m] [name_m]Diesel[/name_m].
Thanks for the comment @southernmaple! Interestingly [name_m]Vin[/name_m] [name_m]Diesel[/name_m]'s real name is [name_m]Mark[/name_m] [name_u]Sinclair[/name_u]!
I don’t think [name_m]Diesel[/name_m] matches very well with [name_f]Rosamund[/name_f], [name_f]Elowen[/name_f], and [name_u]Barrett[/name_u]. [name_m]Diesel[/name_m] just sounds hyper-masculine and it seems ill suited next to your other childrens’ names. I think [name_m]Dietrich[/name_m] could work though!
Definitely not a fan of the name [name_m]Diesel[/name_m]. I just think of cars and petrol stations.
I agree that [name_m]Diesel[/name_m] strikes me first as a) a hyper-masculine name in the vein of [name_m]Gunner[/name_m], [name_m]Blade[/name_m], [name_m]Spike[/name_m], etc. and b) a dog’s name - sorry! I couldn’t see it working with sisters called [name_f]Rose[/name_f] and [name_f]Ella[/name_f], let alone [name_f]Rosamund[/name_f] and [name_f]Elowen[/name_f], which are SO beautiful, delicate and romantic. [name_m]Dieter[/name_m] or [name_m]Dietrich[/name_m] (or Dashiell, or [name_m]Diederick[/name_m], or even [name_m]Dedalus[/name_m]) would fit so, so much better in my view.
[name_m]Diesel[/name_m] is a very interesting name, not the worst name by any means, but comes with lots of connections to other things, and also, like mentioned above doesn’t exactly work with the other names you have. My suggestion is to consider naming your child [name_m]Dieter[/name_m] or Dietrick or [name_m]Dierk[/name_m], and then using [name_m]Diesel[/name_m] as his nickname! Lots of people go by their nicknames all their lives (my Grandpa’s name is [name_m]John[/name_m] but literally everyone calls him [name_u]Merle[/name_u]), and it works just great!
Good luck choosing! 
I like the idea of using [name_m]Diesel[/name_m] as a nn
Reminds me of a guy named [name_m]Rigs[/name_m] I used to know. I thought the name [name_m]Rigs[/name_m] was super cool and masculine. I think his full name may have been Wrigley.
I do like it as a nn, but I don’t think it works as a given name, and [name_m]Dietrich[/name_m] definitely works better with your children’s names.