I was thinking about a V6 Ingenium engine. Easy enough to do, when I saw this.
Jaguar Land Rover Ingenium inline-six cylinder due in 2017 – report

and

Jaguar Land Rover readies Ingenium straight six for launch in 2017 by CAR Magazine

The inline 6 comes in petrol or diesel variants, I guess the glow plugs and spark plugs use the same hole.