Thanks so much for your response and the confirmation that STOU 10W30 will be suitable for both the engine and backend transmission for the International 674. Your time and expertise is much appreciated and has given much peace of mind on the vast subject of tractor lubricants. Ferguson & Menzies came highly recommended and your prompt reply and in depth knowledge not only lived up to expectations but well exceeded them!
With a subject as wide and diverse as engine and transmission oil and how many different oils and advice out there it was great to get expert advice and peace of mind that the tractor has the right oil and quality oil to keep her in good nick!
Thanks again and as recommended will be using the Opus STOU 10W30 for the 674.
All the best