Romania not a German ally?

Greetings. This is my first post on this forum. I have a question.
Some posters on this forum have argued that there was no explicit alliance treaty between Romania and Germany and, therefore, Romania wasn't truly an ally of Germany; other sources claim that Romania wasn't "technically", an ally.
Now, Romania joined the Tripartite Pact initially established by Germany, Japan and Italy; that pact provided for enlargement to other powers (such as Romania) and its Article 3 provided for military cooperation in case of need.
My question is this. Why should Romania not be considered an ally of Germany in WWII, from 1940 to 1944?

Thank you in advance for any reply.

Basically, the allies are not only binded by signed agreements, but by the same goal. For example, the Western Allies had the goal of liberating the countries from under the German occupation and to crush the Nazi Germany.

In the case of Romania, the fighting against USSR alongside Germany was dictated by different reasons, from the ones of Germany.

Hitler told Antonescu that, unlike Great Britain - accused that it deployed forces from its colonies and dominions on the front - he could not expect Romania to take part in the war, merely facilitate the deployment of German troops on its territory. The General's (Antonescu) answer was quick: "the Romanian people would never forgive him if, while the German soldiers were fighting to liberate the Romanian territories annexed by the USSR on June 28th, 1940, the Romanian army was in expectation".

This answer was in full accordance with the national interest, with the national dignity, it was fully concording with the General's belief that a total and loyal cooperation with the Reich - the greatest power on the continent at that time - would allow Great Romania to re-make its borders. Romania's participation in the Eastern Campaign was in the General's view - to bring Bessarabia, Northern Bukovina and the Hertza Country back to Romania; fidelity on the Romanian-German military relationships was to convince Hitler to think over the Vienna Dictate.

http://www.worldwar2.ro/forum/viewtopic.php?t=592
Romania in World War 2 1941-1945, ISOSIM, Bucharest 1997

I wouldn't say that the term of allies, when speaking of German-Romanian relationship, during 1941-44, is wrong, only it is not the classical example of alliance. I think "comrades in arms" is better

The correct term would be "coalition", not "alliance".